Available online at http://docs.lib.purdue.edu/jate
Journal of Aviation Technology and Engineering 1:2 (2012) 63–73
Global Outsourcing of Aircraft Maintenance
D. Scott Worrells
Embry-Riddle Aeronautical University, Worldwide Campus
Before the airlines were deregulated, the majority of air carriers conducted their maintenance in-house. After deregulation, with
competitive pressures mounting and airlines failing and starting up seemingly simultaneously, the outsourcing of maintenance became
more prevalent. Not restricted to U.S. airlines, outsourcing maintenance has become a global practice. Factors involved in the outsourcing
decision range from a startup not having the capital to develop their own in-house maintenance program, to legacy carrier’s cost cutting
efforts, and all points in between. This paper will address specific aspects of the global outsourcing of aircraft maintenance. For the
purposes of this paper, Maintenance, Repair, and Overhaul (MRO) and maintenance are used synonymously.
Keywords: Maintenace Repair Overhaul, Outsourcing, Maintenance
Global Outsourcing of Aircraft Maintenance
For those who study the airline industry, and more specifically, aircraft maintenance, it is a well-known fact that airlines
are not in the aircraft maintenance business. However, the importance of quality, compliant, cost effective maintenance
cannot be overstated. Estimates for the total cost of aircraft maintenance range from 10% to 15% of an air carrier’s budget
About the Authors
Michael McFadden is a professional pilot flying for the fractional ownership provider Netjets. Mr. McFadden received his graduate degree in
Aeronautical Science from Embry-Riddle Aeronautical University in 2011.
D. Scott Worrells is a full time faculty member in Embry-Riddle Aeronautical University’s Worldwide Campus. Dr. Worrells holds a doctoral degree in
Workforce Education and Development from Southern Illinois University Carbondale, and graduate and undergraduate degrees in Management and
Technology-Avionics from Embry-Riddle Aeronautical University.
(Al-Kaabi, Potter, & Naim, 2007). As recently as 2007, the
Federal Aviation Administration (FAA) estimated that
‘‘overall, major air carriers outsourced an average of 64
percent of their maintenance expenses compared to 37
percent in 1996’’ (Department of Transportation, 2008,
p. 1). Airlines continually search for ways to reduce this
expense, and it is the primary factor in the decision to
Economics of scale has an impact on the decision to
outsource maintenance. Each individual airline must
determine the point at which there is a positive return on
the investment in maintenance capability. Large air carriers
with hundreds of aircraft can justify the investment for a
multi-level maintenance capability. However, an airline
with a relatively small fleet may not have the capital,
desire, or need to establish a multi-level maintenance
program. This is particularly true for startup air carriers and
low cost carriers (LCC).
Another factor is the tendency to blend maintenance
capability. All air carriers outsource some element of their
maintenance requirement. Typically, heavy maintenance,
which is labor intensive and requires extraordinary outlay
for facilities and equipment, is outsourced. For carriers in
the US, 71% of heavy maintenance is outsourced, with
engine maintenance one of the fastest growing segments of
the maintenance, repair, and overhaul (MRO) market
(Phillips, 2008). On the other end of the maintenance
spectrum, ground handling, servicing, and organizational
level maintenance is most frequently not outsourced.
Regardless who conducts the maintenance on an airline’s
aircraft, aircraft maintenance is ultimately the responsibility
of the airline (FAA, 2008). Accordingly, the most critical
part of the outsourcing process is selecting a reputable
MRO provider. While high rates of reliability are always
expected, many air carriers are looking for more, such as
total support solutions.
Global MRO Growth and Consolidation
Global MRO revenue in 2002 was between 25 and 30
billion dollars (Czepiel, 2003). Recent economic conditions
have reduced short term estimates of MRO demand;
however, long term growth is forecast at 4.3% through
2018 (Phillips, 2009). From 2002 through 2010, average
spending for MRO was $340.2 billion (see Figure 1). It is
estimated to reach $65 billion by 2020, doubling the 2003
$30 billion estimate by Czepiel.
Projected MRO growth is ‘‘particularly strong in India
and China, followed by Asia, Europe and North America
with less growth in North Africa and the Middle East’’
(Phillips, 2008, para. 9). The North American MRO market
remains largest in dollars spent, at $15.6 billion in 2007,
‘‘followed by Western Europe ($10.4 billion), Asia-Pacific
($5.6 billion), China ($2.3 billion), the Middle East ($2
billion), South America ($2 billion), Africa ($1.5 billion),
Eastern Europe ($1.2 billion), and India ($444 million)’’
(Jackman, 2007, para. 18).
The global recession has contributed to consolidation in
the MRO industry. Lufthansa Technik (LHT) has started a
joint venture with Qantas, opening up LHT Sofia to
overhaul short and medium range aircraft and ‘‘…several
MROs reported forming partnerships with firms in other
regions to offer more competitive costs and convenience to
customers’’ (Moody, 2009, para. 16). Aeroman, the largest
MRO in Central America, sold 80% of the company to Air
Canada Technical Services in 2006 and now operates under
the Aveos brand (Tegtmeir, 2011).
Heavy Maintenance Visits
Heavy maintenance visits (HMV) will grow from $9
billion in 2008 to $13 billion in 2017 (Phillips, 2008).
Industry experts estimate two-thirds of HMV costs are
labor costs (Jackman, 2007). With foreign labor costs less
than 50% of those in the US (see Figure 2), it is easy to see
why many air carriers have shifted their HMV to overseas
providers (Weaver, 2008), with estimated savings at $1
million per aircraft each year (Pandit, 2007).
Delta TechOps Program Manager Beadle concurs,
stating: ‘‘Labor costs represent approximately 70% of
HMV costs’’ (M. Beadle, personal communication,
February 9, 2011). In 2008, starting pay at Aeroman was
approximately $4,500 per year with veterans earning
approximate $15,000. That compares to the U.S. average
of $52,000 (Smith & Bachman, 2008). ‘‘Delta Airlines
sends the majority of wide-body HMV to facilities in the
Far East to take advantage of lower labor costs’’ (M.
Beadle, personal communication, February 9, 2011).
Narrow body HMV work tends to stay in the Western
Hemisphere, with MRO providers in Central America
playing a significant role; lower labor costs and shorter
ferry flights contribute to cost savings.
Figure 1. Estimated world MRO spending. Adapted from ‘‘Airline
maintenance costs executive commentary,’’ 2011, International Air
Transport Association, p. 3.
64 McFadden and Worrels / Journal of Aviation Technology and Engineering
Another factor in the outsourcing equation is the capital
investment in facilities, equipment, and associated over-
head. The hangar space required to shelter an aircraft that is
virtually dissembled is considerable. In addition, the heavy
equipment, work stands, test equipment, support equip-
ment, test benches, etc., represent a considerable outlay of
capital. And, this equipment needs to be maintained and
calibrated on a regular basis, as well. The cost of
establishing a heavy maintenance capability can be
prohibitive, with breakeven return on investment perhaps
10 to 15 years down the road. Another cost consideration is
the maintenance burden, ‘‘administrative and overhead
costs associated with the maintenance function that cannot
be attributed directly to a particular airframe or engine
but allocated on a fairly arbitrary basis’’ (Wensveen, 2007,
Power Plant MRO
Power plant MRO is projected to be the fastest growing
segment of MRO at an estimated annual growth rate of
4.6% (Phillips, 2008). Power plant technology has allowed
for greater reliability and on-wing time. While it would be
natural to assume that this would translate into reduced
costs, that is not necessarily the case; some estimates show
power plant maintenance spending increasing ‘‘two percent
faster than traffic through 2013’’ (Canaday, 2005, para. 30).
The reason for this projected increase is mainly due to the
high cost of repair parts. Costs of repair parts from
‘‘General Electric (GE), Pratt and Whitney (PW) and CFM
International (CFMI) …[are] increasing at an average of
3.5 to 4.5 percent a year’’ (Canaday, 2005, para. 27).
Line maintenance is outsourced much less frequently
than either heavy maintenance or power plant MRO;
however, the outsourcing of line maintenance is primed for
growth. AeroStrategy principal Stewart states: ‘‘Our
analysis estimates that for 2008, about 12 percent of line
maintenance is outsourced, and by 2017, that could reach
as much as 30 percent’’ (as cited in Seidenman, 2008, para.
4). Line maintenance occupies a very special place in the
operation of an airline due to the direct impact it can have
on operational performance, both positive and negative.
Delays at the gate can be expensive, with estimates from
$50 to $100 per minute and an outright cancellation up to
$60,000 (Certified Aviation Services, 2007, para. 17).
Before an airline will outsource such a critical function, it
needs to be assured that a potential vendor would be able to
supply the same level of qualified personnel.
Component Repair and Spare Parts Inventory
Component repair. The outsourcing of component
repair and replacement is also undergoing a significant
degree of transformation. As in other areas of aircraft
maintenance, established airlines once had their own shops
to repair or rebuild components such as landing gear,
auxiliary power units, electrical system components,
hydraulic-pneumatic system components, and various
power plant components. Some even had their own
avionics shops for the repair of communication and
navigation equipment, flight management systems, and
Airlines look for component support solutions that are
flexible, with predictable costs. For example, ‘‘Airtran
outsources its component support to several large vendors,
mostly manufacturers like Honeywell’’ (Canaday, 2005,
para. 69). Borowski, Airtran’s vice-president of main-
tenance and engineering, states: ‘‘We pay a rate per flight
hour, the invoicing is simple, there is very little adminis-
tration, and the costs are predictable’’ (as cited in Canaday,
2005, para. 69).
Spare parts inventory. The cost of inventory runs into
millions of dollars and inventory management is labor
intensive. While these facts have not changed, the
landscape has changed dramatically with airlines reducing
the amount of inventory they hold directly, outsourcing it to
companies dedicated to inventory management. In 2007,
inventories were reduced to 61% from 75% of the $48
billion spare parts inventory previously stocked and stored
(Trebilcock, 2007, para. 2). One airline executive says,
‘‘We continue to see upward trending with airlines
choosing to get out of the inventory management and
repair business’’ (as cited in Moorman, 2011, para. 3).
Figure 2. Estimated man hour costs in dollars. Adapted from ‘‘Tenets of MRO strategy for airlines,’’ by P. Pandit, 2007, p. 6.
McFadden and Worrels / Journal of Aviation Technology and Engineering 65
While the benefits of outsourcing component repair and
inventory management can be considerable, there are risks.
An airline must make sure that it is using a reputable
supplier for not only reliability and timely delivery of the
required items, but for quality and legitimacy of approved
parts, as well.
Production Planning and Control
Airlines have been reluctant to give up control of
production planning and control activities, making them the
least outsourced. That may be changing, according to
House of TIMCO Aviation Services: ‘‘But now that airlines
are accustomed to subcontracting to lower labor cost
providers, many view outsourcing of the back office as the
next cost saving opportunity’’ (as cited in Seidenman &
Spanovich, 2009, para. 1).
As with the other areas of outsourcing, ultimately a
vendor must be able to show that, while they are able to
keep costs under control, they can also effectively manage
the contracted work. Demeis, president and founder of
Continuum Applied Technology, believes that the move to
outsource these important functions may be premature:
Frankly, I don’t think that any savings involved with
outsourcing back office support would be great at this
time, because at least a portion of the carrier’s quality
control department will have to supervise the perfor-
mance of the third-party company. That means that any
savings related by eliminating an internal IT staff
position will be greatly diminished. (as cited in
Seidenman & Spanovich, 2009, para. 20)
All air carrier maintenance programs have their roots in the
initial certification of an aircraft. Design of maintenance
programs must be flexible enough to accommodate air carrier
specific requirements and must comply with Federal Aviation
Regulations (FARs). Most of the world’s airlines and
manufacturers use the Airline/Manufacturer Maintenance
Program Planning Document or Maintenance Steering Group
(MSG) in the development of maintenance programs (Air
Transport, 2003). The Air Transport Association of America
(ATA) administers and maintains this document to provide
guidance on the development of maintenance procedures for
new aircraft. Specifically, the ATA states:
It is the objective of this document to present a means for
developing the scheduled maintenance tasks and inter-
vals which will be acceptable to the regulatory
authorities, the operators, and the manufacturers. The
scheduled maintenance task and interval details will be
developed by coordination with specialists from the
operators, manufacturers, and the Regulatory Authority
of the country of manufacture. Specifically, this
document outlines the general organization and decision
processes for determining scheduled maintenance
requirements initially projected for the life of the aircraft
and/or power plant. (2003, p. 11)
Once these basic regulatory requirements are met, the
FAA provides fairly wide latitude on the specific structure
of an airline’s maintenance operations. According to the
Establishing appropriate standards and regulatory require-
ments is a risk management process and the underlying
legal structure provides for more than one level of
acceptable risk. Air transportation regulations are all-
inclusive and stand alone, whereas the regulations
governing other air commerce do not. Similarly, the
scope of responsibility for those in air transportation is
very broad and not shared, whereas in other air commerce
it is relatively narrow and shared. The regulations in parts
119, 121 and 135 relate directly to air carrier maintenance
programs and reflect the highest possible degree of public
safety. The regulations in parts 43, 65, 91, and 145 do not
necessarily reflect the highest possible degree of safety in
the public interest. (2008, para. 8)
The FAA sets the tone for Air Carrier Maintenance
Programs; it describes in detail how an air carrier may
structure its maintenance program. Advisory Circular (AC)
120-16E describes how a maintenance organization can be
set up for both a FAR Part 121or a FAR Part 135 operation.
The foundation and legal basis for airworthiness and
maintenance of an air carrier’s aircraft is found in FAR Part
121. As stated in FAR Part 121.363:
(a) Each certificate holder is primarily responsible for
(1) The airworthiness of its aircraft, including air-
frames, aircraft engines, propellers, appliances,
and parts thereof; and
(2) The performance of the maintenance, preventive
maintenance, and alteration of its aircraft,
including airframes, aircraft engines, propellers,
appliances, emergency equipment, and parts
thereof, in accordance with its manual and the
regulations of this chapter.
(b) A certificate holder may make arrangements with
another person for the performance of any main-
tenance, preventive maintenance, or alterations.
However, this does not relieve the certificate holder
of the responsibility specified in paragraph (a) of this
section. (Responsibility for Airworthiness, 1973)
By definition, ACs are not mandatory as issued; AC 120-
16E describes ‘‘the scope and content of air carrier aircraft
66 McFadden and Worrels / Journal of Aviation Technology and Engineering
maintenance programs’’ (FAA, 2008, p. i). This AC
describes how an air carrier’s maintenance program
‘‘should reflect three specific program objectives to provide
the highest possible level of safety in air transportation’’
(FAA, 2008, p. 2). These objectives are:
(a) each of your aircraft released to service is airworthy
and has been properly maintained for operations in air
transportation; (b) maintenance and alterations that you
perform, or that other persons perform for you, are
performed in accordance with your maintenance manual;
and (c) competent personnel with adequate facilities and
equipment perform maintenance and alterations on your
aircraft. (FAA, 2008, p. 2)
Advisory Circular 120-16E describes the 10 elements
required of an air carrier maintenance program. These 10
1. Airworthiness responsibility
2. Air carrier maintenance manual
3. Air carrier maintenance organization
4. Accomplishment and approval of maintenance and
5. Maintenance schedule
6. Required Inspection Items
7. Maintenance recordkeeping system
8. Contract maintenance
9. Personnel training
10. Continuing Analysis and Surveillance System
Chapter nine of AC 120-16E describes what is expected
for contract maintenance. The first paragraph of chapter
nine of this AC clearly spells out this responsibility, stating:
Consistent with 121.1 (b), 135.1 (b)(2) and others, when
you use a maintenance provider to accomplish all or part
of the maintenance activities on your airplane or its
component parts, that maintenance provider becomes, in
effect, part of your maintenance organization and under
your control. (FAA, 2008, p. 33)
The Decision to Outsource
Prior to deregulation, most aircraft maintenance was
conducted in-house (vertically integrated) and, according to
Delta TechOps Program Manager Beadle, ‘‘years ago no
one really paid much attention to the cost of aircraft
maintenance. It was all part of doing business’’ (personal
communication, February 9, 2011).
Outsourcing as a business model has become an
accepted way for companies to reduce costs and focus on
core competencies. Sackett and Sakburanapech state:
‘‘Although outsourcing enables companies to focus on
their core competencies and may reduce costs, most
enterprises are cautious about outsourcing business critical
activities’’ (2006, p. 1). Critical outsourcing as shown in
Figure 3 is ‘‘characterized by both high importance and
financial impact’’ (Sakburanapech, 2008, p. 28).
Outsourcing of aircraft maintenance is a business critical
activity with regard to strategic importance and finances.
What makes outsourcing of aircraft maintenance unique is
that lives are potentially at risk if maintenance is not done
Aircraft maintenance is now viewed as a non-core
business. However, this widely accepted definition does not
apply to all areas of outsourced aircraft maintenance; at
least one airline, Jet Blue, considers line maintenance a
core competency. Ramage, vice-president of technical
services, stated: ‘‘Each airline defines what core business
is differently. For Jet Blue, line maintenance is a core
business; heavy maintenance is not’’ (as cited in Schifrin,
2007, para. 28).
Rapid emergence of LCCs in the US and abroad has had
an impact. These air carriers have decided to outsource
maintenance rather than establish maintenance operations
from scratch. The maintenance outsourcing trend is well
established (see Table 1).
Jet Blue’s Director of Maintenance states:
Our business is to fly people safely from one point to the
next. Line maintenance is a requirement. You must have
that if you want reliability. But when you start talking
about MRO, that’s a whole different business. It requires
a lot of overhead and tooling and we leave that to the
experts. They can do it a lot more efficiently than we
can. We’ll stick to our core business. We believe that
will maximize shareholder value. (as cited in
‘‘Maintenance Outsourcing: Emerging,’’ 2009, para. 23)
Figure 3. Outsourcing Classifications. Adapted from ‘‘Development of a
relationship management framework and related performance metrics for
outsourced aircraft maintenance,’’ by A. Sakburanapech, 2008, Cranfield
University, p. 11.
McFadden and Worrels / Journal of Aviation Technology and Engineering 67
Foreign LCCs, one of the fastest growing segments of
the worldwide aviation market, feel much the same way.
Indicative of this is the view of Jetstar Asia’s Head of
Engineering, Neo. Neo indicates that he wants an MRO
provider with ‘‘the capability to provide a full suite of
Engineering services, including a proven and strong ability
to provide AOG [Aircraft on Ground] recovery from
technical breakdowns’’ (as cited in Moody, 2010, para. 24).
With the trend towards outsourcing, a question arises as
to whether an airline should keep the work or send it out.
When evaluating the outsourcing decision, some air carriers
use a Make/Buy decision model to help them determine
whether or not to outsource. Well established as an
accepted course of action in many industries, it provides
management with a tool for determining where work
should be done. According to Smith, ‘‘it is the maximum of
every prudent master of the family, never attempt to make
at home what it will cost him more to make than to buy’’
(as cited in Ferreira & Serra, 2010, para. 1). Is it more cost
effective to have someone else do the required work or is it
better if it is kept in-house? Transaction Cost Economics is
one description of the Make/Buy method. Transaction Cost
Economics is ‘‘fundamentally concerned with the question
of whether it is advantageous, in terms of cost, for
transactions to occur within the hierarchy of an organiza-
tion or externally in the open market’’ (Rieple, 2008, para.
2). According to Program Manager Beadle, Delta TechOps
uses a Make/Buy decision for all of Delta’s maintenance
work, and while TechOps might be given a preference in
getting the bid for some work, if they are not competitive,
the work will in fact be outsourced (personal communica-
tion, February 9, 2011).
The MRO Model
Al-Kaabi et al. (2007) describe four levels of MRO:
Fully Integrated, Partially Outsourced, Mostly Outsourced,
and Wholly Outsourced, as shown in Figure 4. Within
these levels, the entire aircraft maintenance spectrum is
Airline Maintenance Outsourcing (as percentage of total expenses)
Airline 2005 2006 2007 (through Q3)
Alaska 92% 80% 81%
Hawaiian 80% 86% 89%
77% 81% 80%
Northwest 76% 83% 81%
76% 91% 91%
Continental 69% 68% 70%
JetBlue 68% 64% 65%
Southwest 68% 81% 85%
AirTran 66% 93% 94%
Frontier 65% 79% 80%
United 63% 66% 67%
Delta 48% 73% 72%
American 46% 49% 51%
18% 85% 87%
Note. Adapted from ‘‘Outsourcing of airline maintenance sours,’’ by W. J.
McGee, 2008, Consumer Reports, para. 18.
Merged with America West,
Merged with US Airways,
Figure 4. MRO Model Depictions. Adapted from ‘‘An outsourcing decision model for airlines’ MRO activities,’’ by H. Al-Kaabi et al., 2007, Journal of
Quality in Maintenance Engineering, 13(3), p. 220.
68 McFadden and Worrels / Journal of Aviation Technology and Engineering
Fully Integrated MRO
An airline performs all aircraft maintenance activities in-
house. In addition, it may look to sell excess capacity to
This practice is well-suited for airlines with large, varied
fleets and an extensive route structure (Al-Kaabi et al.,
Partially Outsourced MRO
An airline meets a large portion of its needs in-house
with a minimum of outsourcing. This permits a good deal
of flexibility and adaptation to seasonable demands, and is
best suited for airlines that have just a few different fleet
Mostly Outsourced MRO
Most maintenance is outsourced while critical needs are
kept in-house (Al-Kaabi et al., 2007). ‘‘Critical needs’’ are
defined by individual carriers. For example, Jet Blue
Airlines defines line maintenance as critical to its operation
and keeps most of that activity in-house.
Wholly Outsourced MRO
All maintenance is outsourced. This model is used by
startup airlines that do not have the capital to establish an
MRO capability or that choose not to as a part of their
MRO Provider Selection
Perhaps the most important factor to consider is the
selection of the MRO provider. Many variables come into
play and each one must be considered carefully. Wyman
uses a very thorough six-step process that evaluates all
aspects of a provider before making a recommendation to
an airline. These six steps are:
1. Define requirements. Develop a detailed description
of what is to be expected, including the volume and
timing of the work required.
2. Explore and understand the current marketplace.
Knowing who is doing quality and reliable work is
3. Define outsource strategy and require initial bids for
the work. Determine whether or not to bundle/
unbundle services; length of contract; and type of
4. Feedback for bidders. Specific details concerning
pricing and suggestions on ancillary services are
5. Face to face negotiations. Establish terms and
conditions. On-site inspection must be a contract
provision. Conclude with formal Memorandum of
6. Convert MOU into formal, detailed contract. (as cited
in Canaday, 2007, para. 5)
It should be noted here that this last step is recommended
by the FAA in AC 120-16E Chapter Nine as an important
factor in the outsourcing process. The Federal Aviation
When possible, you should have a written contract with
anyone performing maintenance work for you on a
continuing basis. This will help ensure your responsi-
bilities are addressed. In the case of major operations,
such as engine, propeller, or airframe overhaul, the
contract should include a specification for the work. You
should include or reference that specification in your
manual system. (2008, p. 33)
Sakburanapech (2008), describes a process that was
developed by Momme and Hvolby that has three phases
and six activities, as shown in Figure 5.
The actual selection process varies by airline and is
based on needs and priorities set by management.
However, regulatory requirements must be addressed to
Figure 5. The outsourcing process.Adapted from ‘‘Development of a relationship management framework and related performance metrics for outsourced
aircraft maintenance,’’ by A. Sakburanapech, 2008, Cranfield University, p. 15.
McFadden and Worrels / Journal of Aviation Technology and Engineering 69
the satisfaction of the FAA. For example, Becher, a
spokesman for Northwest Airlines stated in 2005:
While costs for outsourced maintenance are lower than
for in-house maintenance, quality and safety are not
compromised.... Northwest selects them because of their
world class management, control systems and technical
ability. Outside vendors undergo a rigorous review
before being offered a maintenance contract by
Northwest. (as cited in ‘‘Maintenance Outsourcing,’’
2009, para. 14)
Jet Blue’s vice-president of technical services, Ramage,
uses turnaround times and the quality of service as key
factors in the selection process. He said ‘‘The first thing we
look at is the culture of the company. And obviously when
I talk about quality, it is what the safety culture is and can
they do the job well. Quality, safety and experience is
important’’ (as cited in Arnoult, 2010, para. 7).
The Oversight Process and its Contribution to Safety
Air Carrier Oversight
The first line of defense in prevention of errors that may
lead to improper maintenance is an air carrier’s CASS.
Required by FAR Part 121.373, CASS is one of the 10
elements of a maintenance program (Continuing Analysis
and Surveillance, 1996):
The high level purpose of a CASS is to reduce or
eliminate the likelihood of your aircraft being approved
for return for service when it is not airworthy through the
continuous, system safety-based, closed loop cycle of
surveillance, investigation, data collection, analysis,
corrective action, monitoring, and feedback of a
CASS. (FAA, 2010, p. 6)
Four basic activities of CASS are: surveillance, analysis,
corrective action, and follow up. Encompassed therein are
audit processes, data collection processes, Root Cause
Analysis (RCA), and performance measurement. This risk-
based, closed loop system verifies performance and
effectiveness of a maintenance program (see Figure 6)
U.S. repair stations. Problems with FAA oversight of
outsourced maintenance and contract repair stations drew
attention from Department of Transportation’s (DOT’s)
Office of Inspector General, the public, and the U.S.
Congress. The catalyst for this attention was the crash of
ValuJet Flight 592 into the Florida Everglades in May,
1996. The ValuJet accident was one of three fatal airline
accidents related to contract maintenance (Adams, 2009).
The ValuJet accident investigation ultimately laid blame at
the feet of the Sabre-Tech (the contract maintenance
provider), ValuJet, and the FAA (National Transportation
Safety Board, 1997).
International repair stations. The U.S. and select
foreign countries recognize each other’s aviation safety
standards and programs through Bilateral Aviation Safety
The purposes of this Agreement are to: (a) enable
reciprocal acceptance of findings of compliance and
approvals issued by the Technical Agents and Aviation
Authorities; (b) promote a high degree of safety in air
transport; and (c) ensure continuation of high level
regulatory cooperation and harmonization between US
and EC. The scope of cooperation under this Agreement
is: (a) airworthiness approvals and monitoring of civil
aeronautical products; (b) environmental testing and
approvals of civil aeronautical products; and (c)
Figure 6. Four Basic CASS Activities. Adapted from ‘‘Developing and implementing an air carrier continuing analysis and surveillance system,’’ 2010,
FAA AC 120-79A p. 15.
70 McFadden and Worrels / Journal of Aviation Technology and Engineering
approvals and monitoring of maintenance facilities.
(Council of the European Union, 2011)
Certified/non-certified repair stations. Certification of
Part 145 repair stations is subject to regulatory require-
ments of the FAA; non-certificated stations are not (see
Air carriers ensure through proper audits and oversight
that contracted facilities perform according to approved
maintenance programs. According to the DOT: ‘‘Non-
certificated facilities performing critical maintenance cre-
ates a double standard because certificated repair stations
are required to have designated supervisors, inspectors,
return-to-service personnel, and quality control systems.
No such requirements apply to non-certificated facilities’’
(DOT, 2005, p. 6). A DOT investigation found:
…as many as 1,400 domestic and foreign facilities that
could perform the same work (e.g., repairing flight
control systems and engine parts) a certificated facility
performs but are not inspected like certificated facilities.
Of those 1,400 facilities, we identified 104 foreign non-
certificated facilities—FAA had never inspected any of
them. (2005, p. 6)
Contract maintenance is as old as the aviation industry
itself. Over time, and as the aviation industry has evolved,
the airline industry has integrated contract maintenance into
a post-deregulation business model that emphasizes its core
business, transporting passengers/cargo from point to point,
while marginalizing, to the greatest extent possible, the cost
of aircraft maintenance. Worldwide MROs have grown, in
response to continuous and increasing demand, into a
viable segment of the aviation industry. Proliferation of
MRO facilities worldwide should continue, although
growth has slowed as a result of current economic
stagnation, as long as the industry and the regulators meet
their responsibility to ensure aircraft are maintained to the
high standards required by regulation and good business
Adams, C. (2009, June 1). Maintenance outsourcing safety debate.
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