Specifically, DOD policy requires the services to develop and implement a  sustainment strategy, such as a Life-cycle Sustainment Plan, for  sustaining its weapon systems. We found that 6 of 12 fixed-wing aircraft—3 from  each service—experienced decreased aircraft availability between fiscal  years 2011 and 2016. Navy Aircraft Availability Trends and O&S Cost Trends Varied across the Selected Fixed-Wing Aircraft

			Navy Aircraft Availability Trends Varied, and Five of Seven Aircraft Generally Did Not Meet Availability Goals since 2011

Our analysis found that: between fiscal years 2011 and 2016, aircraft availability increased for  three of the seven Navy fixed-wing aircraft, fluctuated for one, and  decreased for the remaining three aircraft; between fiscal 2011 and 2016, one aircraft met aircraft availability  goals in each year, and four aircraft met goals in some years, while  two aircraft did not meet goals in any of the years; and  in fiscal year 2016, the Navy did not meet aircraft availability goals for  five of the seven aircraft. Also, the  Navy has experienced varying O&S and maintenance costs since fiscal  year 2011 for these aircraft. Sustainment Strategies Were Documented for Some but Not All Aircraft, and the Air Force and Navy Have Other Efforts to Review and Improve Aircraft Availability

The Air Force has documented sustainment strategies for its five selected  aircraft in our review, but the Navy has not documented sustainment  strategies or updated the strategies for four of seven of its aircraft in our  review. In May 2017, the Air Force updated its sustainment guidance to require  sustainment strategies for legacy systems and for those strategies to be  updated every 5 years. This instruction explicitly states that the requirement to document a  sustainment strategy and update it every 5 years is applicable to all  weapon systems, including legacy systems that are in the O&S phase of  their life cycles. Specifically, Navy guidance does not explicitly  state that documenting a sustainment strategy and updating that strategy  every 5 years is a requirement for legacy systems. Until DOD and the Navy update or issue  new guidance clarifying the requirements for documenting sustainment  strategies for legacy systems, weapon system program offices, such as  those for fixed-wing aircraft, as well as Naval Air Systems Command and DOD may not have full visibility of necessary requirements to achieve  program objectives or any related risks associated with the sustainment  of these weapon systems. While the DOD policy and Navy guidance is unclear, Naval Air Systems  Command and Navy program offices for the four aircraft—C-2A, E-2C,  EA-18G, and F/A-18A-D—that either do not have a sustainment strategy  or have not updated the strategy within the last 5 years are taking actions  to document or update the sustainment strategies for these aircraft. The Air Force and Navy Regularly Reviewed Sustainment Metrics and Implemented Improvement Plans to Address Aircraft Availability

The Air Force and the Navy have (1) regularly reviewed sustainment  metrics for fixed-wing aircraft and (2) implemented improvement plans to  address aircraft availability. The Air Force and  Navy share a variety of sustainment challenges, including the age of their  aircraft as well as maintenance and supply support issues. DOD is in the process of taking action  to implement these recommendations. This public  report omits the information that DOD deemed to be sensitive. This report is a public version of a sensitive report that we issued on April 25,  2018. Operating and Support Costs

	Program Office Comments

Appendix XIV: Scope and Methodology

To examine the trends in aircraft availability and operating and support  (O&S) costs for selected Air Force and Navy fixed-wing aircraft, including  whether the aircraft met availability goals, we selected a nongeneralizable  sample of 12 fixed-wing aircraft managed by the Departments of the Air  Force and the Navy. With respect to O&S costs,  we collected and analyzed data from fiscal years 2011 through 2016.
Why GAO Did This Study

DOD spends billions of dollars annually to sustain its weapon systems to support current and future operations. The Air Force and Navy are operating many of their fixed-wing aircraft well beyond their original designed service lives and therefore are confronted with sustainment challenges.
House Report 114-537 included a provision for GAO to evaluate the sustainment of major weapon systems. This report, among other things, (1) examines the trends in availability and O&S costs for selected Air Force and Navy fixed-wing aircraft since fiscal year 2011, including whether they met availability goals, and (2) assesses the extent that the departments documented sustainment strategies, reviewed sustainment metrics, and implemented plans to improve aircraft availability. GAO selected a nongeneralizable sample of 12 fixed-wing aircraft by considering a variety of factors, such as the type, age, and manufacturer of the aircraft, among other factors, and analyzed condition and availability data, O&S costs, and sustainment challenges from fiscal year 2011 through March 2017 for each aircraft in a “Sustainment Quick Look.” GAO also analyzed policies, strategies, and plans, and interviewed Navy and Air Force officials in program offices, squadrons, and maintenance depots.

What GAO Found

Between fiscal years 2011 and 2016, the Air Force and Navy generally did not meet aircraft availability goals, and operating and support (O&S) cost trends for GAO's selected fixed-wing aircraft varied. Specifically, GAO found that
availability declined for 6 of 12 aircraft—3 from each service—between fiscal years 2011 and 2016;
availability fell short of goals for 9 of 12 aircraft in fiscal year 2016; and
O&S costs increased for 5 of the aircraft, and maintenance costs—the largest share—increased for 8 of 12 aircraft.
GAO found, and officials agreed, that these aircraft face similar challenges.
a Obsolescence means a part is unavailable due to its lack of usefulness or it is no longer current or available for production.
b Diminishing manufacturing sources is a loss or impending loss of manufacturers or suppliers.
The Air Force and Navy have documented sustainment strategies for some aircraft, regularly reviewed sustainment metrics, and implemented improvement plans. The Air Force has documented sustainment strategies for all aircraft GAO reviewed; however, the Navy has not documented or updated its sustainment strategies for four aircraft. Specifically, the Navy does not have a documented sustainment strategy for the C-2A, and has not updated the strategies for the E2C, EA-18G, and F/A-18A-D since before 2012. The Navy is in the process of documenting its strategies, but Department of Defense (DOD) policy is unclear on whether a sustainment strategy is required and has to be updated every 5 years for weapon systems that are in the operations and support phase of their life cycle (i.e., legacy systems). Also, Navy guidance does not specify a requirement for legacy systems, although Air Force guidance does. Clarifying the requirements to document sustainment strategies for legacy systems, and documenting those strategies, would add additional visibility over the availability and O&S costs of DOD aircraft and any associated sustainment risks.
This is a public version of a sensitive report issued in April 2018. Information on aircraft availability and other related information was deemed to be sensitive and has been omitted from this report.

What GAO Recommends

GAO is recommending that DOD and the Navy update or issue new policy and guidance clarifying the requirements for documenting sustainment strategies for legacy weapon systems. DOD concurred with the recommendations.