The inventories of the selected Air Force and Navy fixed-wing aircraft in our review totaled 2,823 aircraft and required approximately $20 billion to operate and support in fiscal year 2016. The inventory, aircraft status, initial operational capability, and service life forecast for each of the 12 selected fixed-wing aircraft are shown in figure 1. Sustainment of fixed-wing aircraft and other weapon systems comprises the logistics and personnel services required to maintain and prolong operations, and DOD policy provides direction to service components on sustainment planning across the life cycle of the weapon system. 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. According to DOD’s policy, this strategy should be the basis for all sustainment efforts, including sustainment metrics mapped to key performance parameters and key system attributes, such as aircraft availability, to manage sustainment performance. The policy states that, after initial operating capability, programs should update the sustainment plan whenever there are major changes to its strategy for sustaining the weapon system, or every 5 years, whichever occurs first. The Air Force and the Navy also have guidance that implements the requirements of the DOD guidance. These services’ guidance include sustainment-planning requirements for life-cycle sustainment and assurance of affordability. There are a variety of DOD offices that have roles and responsibilities related to sustaining fixed-wing aircraft. For instance, the Under Secretary of Defense for Acquisition and Sustainment (USD ), is the principal staff assistant and advisor to the Secretary of Defense for all matters concerning acquisition and sustainment. Specifically, USD (A&S) is responsible for establishing policies for logistics, maintenance, and sustainment support for all elements of DOD, including fixed-wing aircraft. The Assistant Secretary of Defense for Logistics and Materiel Readiness (ASD ) serves as the principal staff assistant and advisor to the USD (A&S) on logistics and materiel readiness within DOD. Specifically, the ASD (L&MR) is responsible for (1) establishing DOD policies and procedures for logistics, maintenance, materiel readiness, strategic mobility, and sustainment support; (2) providing related guidance to the Secretaries of the military departments, including developing the Life- cycle Sustainment Plan outline; and (3) monitoring and reviewing programs associated with these areas, among other duties and responsibilities. For the Air Force, the Air Force Materiel Command develops, acquires, and sustains weapon systems through research, development, testing, evaluation, acquisition, maintenance, and program management of the systems and their components. This command provides acquisition and life-cycle management services and logistics support, among other things. The Air Force Life Cycle Management Center within the Air Force Materiel Command is responsible for the life-cycle management of weapon systems from inception to retirement. A Program Executive Officer—responsible for managing a specific portfolio of weapon systems—is responsible for each of the selected fixed-wing aircraft. The Program Executive Officer oversees the program office that manages each weapon system. For the Navy and Marine Corps, the Naval Air Systems Command is responsible for providing the full life-cycle support of naval aviation aircraft, weapons, and systems. This support includes research, design, development and systems engineering; acquisition; test and evaluation; training facilities and equipment; repair and modification; and in-service engineering and logistics support. As with the Air Force, Program Executive Officers oversee their assigned program managers. DOD relies on program managers to lead the development, delivery, and sustainment of individual weapon systems through their life cycles. The program managers are the designated individuals with responsibility for and authority to accomplish the program’s sustainment objectives to meet the users’ operational needs. Product support managers, who work within the program offices, are responsible for developing and implementing support strategies for weapon systems that maintain readiness and control life-cycle costs. Weapon systems are sustained under various arrangements that may include contractors, DOD organic facilities, or some combination of the two. For example, the Air Force Sustainment Center provides depot maintenance through its Air Logistics Complexes for weapon systems. Naval Air Systems Command is responsible for the Navy Fleet Readiness Centers, which provide depot-level maintenance for Navy and Marine Corps fixed-wing aircraft. Additionally, the Air Force Sustainment Center and the Navy Supply Systems Command, as well as the Defense Logistics Agency, manage inventories of repair parts, and individual weapon systems programs are typically supported by a complex supplier network that includes a prime contractor, subcontractors, and various tiers of parts suppliers. On the other hand, sustainment responsibilities—in their entirety or particular elements—may be contracted out as part of a public-private partnership or a performance-based logistics agreement, such as with the F-22 Raptor. The Air Force and Navy monitor the readiness status of selected fixed- wing aircraft through numerous performance metrics. Specifically, the Air Force measures how well a fleet is performing by calculating the availability of the fleets’ aircraft, which is the number of aircraft that are available for flight operations. The Navy measures its aircraft availability through two metrics: (1) Ready-Basic-Aircraft (RBA)—the number of aircraft that are able to safely fly—and (2) Ready-for-Tasking (RFT)—the number of aircraft that are able to conduct specific missions. Both the Air Force and Navy have established goals associated with aircraft availability. In addition to measuring the availability of the aircraft against the associated goals, the Air Force and Navy track the reasons for aircraft not being available or able to conduct missions. Specifically, the Air Force and Navy track the following: Aircraft in depot: Aircraft unavailable to conduct missions because of scheduled or unscheduled depot maintenance or modification. Not mission capable maintenance: Aircraft that are not in depot and not capable of performing any of their assigned missions because of maintenance. Not mission capable supply: Aircraft that are not in depot and not capable of performing any of their assigned missions because of the lack of a repair part. In addition to these three metrics, the Air Force also tracks the following: Not mission capable for both supply and maintenance: Aircraft that are not in depot and not capable of performing any of their assigned missions because of both maintenance and the lack of a repair part. Units possessed not reported: Aircraft that are not available for use for reasons other than depot and not mission capable status, but possessed by the squadron. There are various costs associated with operating and supporting weapon systems. DOD’s Operating and Support Cost-Estimating Guide provides direction to the service components on developing estimates to support various analyses and reviews throughout the program life cycle. According to the guide, as a program matures, it remains necessary to continue to track and assess O&S costs and trends to ensure that the program remains sustainable, affordable, and properly funded. Each military department maintains a database that collects historical data on the O&S costs for major fielded weapon systems. DOD’s Office of Cost Assessment and Program Evaluation provides policy guidance on this requirement, known as the Visibility and Management of Operating and Support Costs program; specifies the common format in which the data are to be reported; and monitors its implementation by each of the military departments. O&S costs are categorized using the following six overarching elements: unit level manpower—cost of operators, maintainers, and other support manpower assigned to operating units; unit operations—cost of unit operating materiel such as fuel, and training material, unit support services, and unit travel; maintenance—cost of system maintenance including depot- and sustaining support—cost of system support activities that are provided by organizations other than the system’s operating units; continuing system improvements—cost of system hardware and software modifications; and indirect support—cost of activities that provide general services that lack the visibility of actual support to specific force units or systems. For the selected Air Force and Navy fixed-wing aircraft in our review, aircraft availability and O&S cost trends varied over the 6-year period between fiscal years 2011 and 2016, and the aircraft generally did not meet availability goals. We found that 6 of 12 fixed-wing aircraft—3 from each service—experienced decreased aircraft availability between fiscal years 2011 and 2016. One aircraft met availability goals each year between fiscal year 2011 and 2016. Conversely, six aircraft met the goals in some years but not others, and five aircraft did not meet the goals in any year. In the latest year included in our review—fiscal year 2016—9 of 12 of the fixed-wing aircraft did not meet their associated availability goals. With respect to O&S costs, the overall O&S total for all 12 aircraft was about $20 billion annually over the 6-year period; some aircraft experienced increases while the costs to operate and support others decreased. The reasons for changes in costs included increases in maintenance costs for 8 of 12 fixed-wing aircraft. Below we summarize these trends, and the “Sustainment Quick Looks” in appendices II–XIII provide detailed information on the trends associated with each of the 12 fixed-wing aircraft and appendix XV provides additional information on operating and support cost per aircraft. Our analysis found that: between fiscal years 2011 and 2016, aircraft availability for two of five selected Air Force fixed-wing aircraft fluctuated and for three decreased; between fiscal 2011 and 2016, two aircraft met availability goals in some years, and three aircraft did not meet availability goals in any of the years; and in fiscal year 2016, four of the five aircraft did not meet availability goals. Specific details regarding aircraft availability and not mission capable status for maintenance, supply, and both maintenance and supply were omitted because DOD deemed this information as sensitive (i.e., For Official Use Only). According to officials, when aircraft availability goals are not met, training and operational missions may not be fulfilled as timely as needed. For example, F-22 squadron officials explained that the lack of available aircraft creates a shortage of trained pilots. F-22 pilots need extensive training to fulfill their air-superiority role. Further, command officials explained that when aircraft availability goals are not met, there may not be enough aircraft to respond to contingency requirements. Officials expressed concern that, given the capability and expectation of the F-22 to be available to create air superiority in any operation, missions may not be met. Additionally, E-8C program office officials stated that missions are often limited to top priority, which means supported combatant commands may not obtain all needed capabilities, such as the E-8C not being able to provide surveillance capability to particular combatant commands. From fiscal years 2011 through 2016, O&S costs for the Air Force aircraft in our review totaled about $13 billion annually. These costs decreased for the C-17, F-16, and the F-22, but increased for the B-52 and E-8C, as shown in figure 2. For example, the F-16’s total annual O&S costs decreased by about $943 million (or about 19 percent) because of decreases in all cost elements—the largest decrease being unit operations—except sustaining support. According to officials, the decrease in unit operations can be attributed to the retiring of aircraft and the consolidation of squadrons. The C-17’s and F-22’s O&S costs decreased mainly because of decreases in two cost elements: continuing system improvements and unit operations. In contrast, the B-52’s and the E-8C’s O&S costs increased, by $76 million (or about 6 percent) and $41 million (or about 6 percent), respectively. The increases occurred because two of the cost elements—continuing system improvements and maintenance costs—increased more than the other costs elements decreased. Based on our analysis of the O&S cost elements, maintenance cost generally is one of the largest portions—on average about 36 percent—of total O&S costs for each aircraft. As shown in figure 3, maintenance costs for four of the five aircraft generally have increased from fiscal years 2011 through 2016. Specifically, maintenance costs for the C-17, E-8C, and F- 22 increased because of additional depot maintenance needs. B-52 maintenance costs fluctuated year to year, but increased overall during this period. The overall maintenance costs for the F-16 decreased by approximately $140 million. According to our analysis, even though there was an increase in some of the F-16 maintenance cost elements, the fleet’s executed flying hours decreased. Therefore, the flying hour depot- level reparable costs decreased by approximately $123 million and engine repair decreased by $115 million, causing the overall maintenance cost to decrease. 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. Specific details regarding aircraft availability and not mission capable status for maintenance and supply were omitted because DOD deemed this information as sensitive (i.e., For Official Use Only). To address decreases in aircraft availability, the Navy has moved available aircraft between squadrons to help ensure deploying squadrons are fully equipped for their assigned missions. In November 2017, the Commander of Naval Air Forces testified before the House Armed Services Committee that to equip the air wings with the required number of mission capable aircraft for the deployment of three aircraft carriers in 2017, the Navy had to transfer 94 strike fighters to and from the maintenance depots or between squadrons. This transfer included pulling aircraft from fleet replacement squadrons, where the focus should be on training new aviators. The Commander of Naval Air Forces, in his November 2017 testimony, summarized the issue: “That strike fighter inventory management, or shell game, leaves non-deployed squadrons well below the number of jets required to keep aviators proficient and progressing toward their career qualifications and milestones, with detrimental impacts to both retention and future experience levels.” Furthermore, based on our analysis, F/A- 18A-D squadrons have underexecuted their flight hours by an average of 4 percent from fiscal years 2011 through 2016. According to officials, this is largely due to low aircraft availability. Additionally, placing further strain on aircraft availability, the F/A-18A-D inventory has decreased from 581 aircraft in fiscal year 2011 to 537 aircraft in fiscal year 2016. From fiscal years 2011 through 2016, O&S costs for the Navy’s seven selected fixed-wing aircraft totaled about $7 billion annually. Also, the Navy has experienced varying O&S and maintenance costs since fiscal year 2011 for these aircraft. Specifically, annual O&S costs decreased for the AV-8B, C-2A, E-2C, and F/A-18A-D, and increased for the E-2D, EA- 18G, and F/A-18E-F, as shown in figure 4. We found that O&S costs for the F/A-18A-D decreased by about 22 percent from about $3.1 billion in fiscal year 2011 to about $2.4 billion in fiscal year 2016. According to officials, this decrease can be attributed to the decrease in inventory as aircraft are retired and squadrons transition to the F-35 Joint Strike Fighter. In another example, O&S costs for the E- 2D increased from about $1.6 million in fiscal year 2012 to about $125 million in fiscal year 2016. The size of the fleet has increased by 17 aircraft—from 3 to 20 since fiscal year 2011. According to officials, this aircraft remains in production with a projected fleet size of 75; as inventory increases, so will O&S costs. Based on our analysis of the O&S cost elements, maintenance cost generally is one of the largest portions—about 42 percent—of total O&S costs for the seven aircraft in our review. Annual maintenance costs have increased for the C-2A, E-2D, EA-18G, and F/A-18E-F, and decreased for the AV-8B, E-2C, and F/A-18A-D, as shown in figure 5. We found that maintenance cost for the C-2A increased by about 7 percent from about $89 million in fiscal year 2011 to about $95 million in fiscal year 2016. According to officials, the increase in maintenance cost can be attributed to increased demand for outer wing panels, which resulted in a $16 million increase in depot-level repair costs and a more than 10 percent increase in executed flight hours, among other things. In another example, maintenance cost for the AV-8B decreased by about 9 percent from about $375 million in fiscal year 2011 to about $341 million in fiscal year 2016. According to officials, these decreases can be attributed to the AV-8B no longer being used in Operation Enduring Freedom in 2012, the loss of six aircraft, and the transition of AV-8B squadrons to the F-35 Joint Strike Fighter. The Air Force and Navy face similar sustainment challenges that relate to aging, maintenance, and supply support that affect aircraft availability and O&S costs for the 12 aircraft selected in our review, as shown in figure 6. Specifically, 10 of 12 aircraft are experiencing sustainment challenges related to aging; all 12 are experiencing challenges related to maintenance; and all 12 are also experiencing challenges related to supply support. Below is a brief overview of these challenges: Aging: A number of these aircraft are aging and operating beyond their planned service life, partly because of delays in replacement aircraft. Specifically, the Air Force and Navy plan to replace the F-16, AV-8B, and F/A-18A-D with the F-35 Joint Strike Fighter. The Navy is expected to transition the F/A-18A-D through 2030 and the Marine Corps is planning to use the F/A-18A-D beyond 2030 (although these time frames have been extended several times already). The Navy plans to retire the AV-8B in 2026. On the other hand, the Air Force is not expected to retire the F-16 until at least 2040. Because of aging, according to officials, there are parts on some aircraft that need to be repaired and replaced that were not accounted for during initial sustainment analysis. To mitigate some challenges associated with the age of the fixed-wing aircraft, the Air Force and Navy program officials have decided to extend the service life of some aircraft by repairing and overhauling airframes and components, as well as developing the engineering specifications for parts that were never planned to be repaired or replaced. Maintenance: Delays in getting aircraft into and through depot maintenance, as well as shortages of skilled maintainers, are contributing to some aircraft missing their availability goals. Both services reported losing experienced maintainers, either to retirement or to other programs such as the F-35 Joint Strike Fighter. To address maintenance challenges, program offices for the selected aircraft have improved the efficiency and speed of depot maintenance, as well as are working to ensure there are sufficient numbers of trained maintainers. Supply Support: Some aircraft are encountering supply shortages as a result of parts not being available, in some cases due to obsolescence issues or diminishing manufacturer sources. Overcoming part shortages through either searching for replacement parts or reengineering parts takes time, which can contribute to aircraft being unavailable for longer periods. To mitigate supply challenges, officials have proactively upgraded aircraft before obsolescence occurs or located available parts and reengineered parts that are no longer in production, as well as identified suitable manufacturers in advance, among other things. For more specific information on sustainment challenges related to aging aircraft, maintenance, and supply support for each of the fixed-wing aircraft, see the “Sustainment Quick Looks” in appendixes II–XIII. 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. The Air Force and Navy also regularly reviewed sustainment metrics and have implemented plans to improve aircraft availability. The Air Force has documented sustainment strategies for the five selected fixed-wing aircraft and updated them in accordance with Air Force guidance. However, the Navy has not documented a sustainment strategy or updated the strategies for four of the seven aircraft in our review since 2012. See figure 7 for the year of the most recent update to the sustainment strategy for the aircraft in our review. While sustainment strategies do not guarantee successful outcomes, they serve as a tool to guide operations as well as support planning and implementation of activities through the life-cycle of the aircraft. Specifically, at a high-level the strategy is aimed at integrating requirements, product support elements, funding, and risk management to provide oversight of the aircraft. For example, these sustainment strategies can be documented in a life-cycle sustainment plan, postproduction support plan, or an in-service support plan, among other types of documented strategies. Additionally, program officials stated that an aircraft’s sustainment strategy is an important management tool for the sustainment of the aircraft by documenting requirements that are known by all stakeholders, including good practices identified in sustaining each aircraft. For example: The strategy for the Air Force B-52 has been updated several times in recent years because of several major modifications. For example, in 2014 the Air Force issued an updated sustainment plan within the life- cycle management plan to update the combat network communications technology program because the B-52’s communications system is still the original from the 1950s and has limitations related to making mission or target changes in flight. The plan addresses the testing, resource management, and numerous program performance indicators and requirements of the system. The strategy for the Air Force F-16 outlines plans for the aircraft’s service life extension and includes proactive measures and data forecasting to bundle depot modifications in order to minimize fleet- wide effects on aircraft availability. The service life extension for the F- 16 is designed to extend the service life of 300 F-16 aircraft from 8,000 to 13,856 flight hours at an estimated cost of $740 million (as of June 2016). The strategy for the Navy E-2D provides a systematic approach to ensure that a comprehensive support package is in place to support the sustainment of the aircraft. Also, it describes the overall plan for the management and execution of the product support package by communicating the sustainment strategy to stakeholders in the acquisition, engineering, and logistics communities. However, the Navy had not documented a sustainment strategy for the C- 2A because a strategy was not required when the aircraft, now a legacy system, was going through the acquisition process prior to 1965. According to Navy officials, while they have not documented a strategy for the C-2A, they are undertaking efforts, such as updating technical publications, performing maintenance analysis on the landing gear, and evaluating depot tasks to decrease turnaround time, among other efforts, to sustain the aircraft. However, a documented sustainment strategy for the C-2A would help guide the planning and implementation of these efforts, as well as serve as a management tool by documenting these requirements that are known by all stakeholders. In addition, the Navy’s sustainment strategies for the E-2C (2011), EA- 18G (2006), and F/A-18A-D (2001) were developed prior to 2012 and thus have not been updated in over 5 years. With respect to the EA-18G, Navy officials told us that the sustainment strategy should be updated in accordance with DOD’s acquisition policy—DOD Instruction 5000.02— since the EA-18G is still in the acquisition process, as it continues to be produced. For the E-2C and F/A-18A-D, Naval Air Systems Command officials and program office officials told us that they were not required to document sustainment strategies because these aircraft were legacy systems at the time the requirement to develop and maintain a sustainment strategy was implemented. Therefore, according to these officials, the DOD requirements to document and update sustainment strategies every 5 years in DOD Instruction 5000.02 were not applicable. DOD Instruction 5000.02 requires weapon systems to have some form of a sustainment strategy that is not older than 5 years; however, it is unclear whether this policy is applicable to legacy weapon systems. Specifically, the policy states that program managers for all programs are responsible for developing and maintaining a sustainment strategy, such as a Life-cycle Sustainment Plan, beginning at the risk-reduction decision point (i.e., Milestone A of the acquisition process). However, based on our discussions with Navy program officials for our selected aircraft and our review of the policy, it is unclear whether the policy—as currently written—is applicable to legacy systems that were no longer in production and thus had completed the risk-reduction decision point (or Milestone A) prior to the requirement to update a sustainment strategy every 5 years. According to DOD officials, the intent of the policy is for all programs, including legacy weapon systems, to develop and maintain a sustainment strategy; however, the policy does not explicitly state that legacy systems are expected to fulfill this requirement. 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. Air Force officials told us that they did this because the DOD policy was unclear whether it was applicable to legacy systems and it was a good practice to ensure the guidance was explicit for all weapon systems to document and update a sustainment strategy. 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. Additionally, the Air Force Instruction states that these legacy systems are not required to retroactively meet requirements identified for previous phases of the acquisition life-cycle, but should meet the requirements needed for continued operations of the system. However, the Navy has not made the requirement explicit for legacy systems in its guidance. 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. While Navy guidance requires the development and use of sustainment metrics for legacy systems and requires the Naval Air Systems Command be responsible for aviation weapon systems in sustainment, the Navy does not address any requirement for sustainment strategies for legacy systems. The lack of clarity in DOD Instruction 5000.02 and the Navy guidance regarding whether legacy systems are required to document a sustainment strategy and update that strategy every 5 years has resulted in confusion regarding sustainment planning requirements among Navy program offices and could cause confusion with other weapon system program offices across DOD. Standards for Internal Control in the Federal Government state that management should define objectives in specific terms so they are understood at all levels of the entity. The standards also state that guidance should clearly define what is to be achieved, who is to achieve it, how it will be achieved, and the time frames for achievement. As indicated by the Air Force’s 2017 update to its sustainment guidance, clarifying DOD and Navy guidance and the applicability of sustainment strategy requirements to legacy systems could be done through very small additions and clarifications to the applicable guidance documents. 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. According to Naval Air Systems Command officials, once it was brought to their attention that the intent of DOD Instruction 5000.02 was for legacy systems to have an updated documented sustainment strategy, they began to take action to develop or update the respective sustainment strategies. Specifically, according to C-2A, E-2C, and E-2D program officials, they are currently updating the E-2D strategy for its 5-year update, which is due in fiscal year 2018, and it will include updates for the C-2A and E-2C since the airframe for all three aircraft are very similar. Also, program officials for the EA-18G and F/A-18A-D told us that they are currently updating the strategies for these aircraft and are expected to complete the process in fiscal year 2018. Given that the Navy is already taking action to update its sustainment strategies and has established timelines for these updates, we are not making any recommendations to the Navy regarding updating the respective sustainment strategies. 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 have regularly monitored the condition of their fixed-wing aircraft, which includes measuring aircraft availability against planned goals as well as monitoring other sustainment metrics. Specifically, the Air Force Materiel Command monitors aircraft availability and other sustainment metrics through quarterly Weapon System Enterprise Review (WSER) briefings. The program office in conjunction with the Air Force Life Cycle Management Center generates the WSER, which is briefed through Air Force Materiel Command and the Program Executive Offices to the Air Force Chief of Staff. The WSER delivers insight into the comprehensive health of a system by flagging gaps in performance and identifying mitigating actions, which is used to conduct crosscutting enterprise analysis and provide input into readiness reviews. In addition to the WSER, the program offices manage their performance through their Health of the Fleet briefs. These briefs—conducted monthly or quarterly depending upon the aircraft—include readiness assessments that provide insight on maintenance and management practices. The assessment is delivered by the program’s maintenance group, and includes aircraft performance metrics, issues, actions, and schedules to inform program leadership on fleet status and to help prioritize and make decisions concerning the issues. The Navy monitors aircraft availability through its aircraft status dashboard for each aircraft, which provides specific information, such as goals, actual availability, and gaps between the two. More specifically, the Navy tracks the status of each of its aircraft through the dashboard, including those aircraft that are available (i.e., Ready-Basic-Aircraft ), are in depot maintenance, or are not mission capable due to maintenance or supply, among other metrics. The dashboard is updated monthly, and there are weekly meetings with key stakeholders, including Naval Air Systems Command officials, industry partners, and depot officials, to monitor the performance of each aircraft and make adjustments to improve aircraft availability. Additionally, all program offices have processes in place to manage the fleet within their portfolios, including semiannual or annual program reviews such as Program Management Reviews and Executive Steering Reviews. These reviews focus on readiness, cost drivers, and initiatives to address program risk and ways to resolve issues affecting each aircraft. Further, the Marine Corps Commandant for Aviation leads biannual Executive Steering Summits to assess readiness issues affecting Marine Corps aircraft. The Air Force and Navy have implemented improvement plans to address aircraft availability for each of the selected fixed-wing aircraft. Air Force program offices for the fixed-wing aircraft in our review have plans for improving availability. Since 2005, the Air Force Materiel Command has had an annual process to improve aircraft availability, which is known as the Aircraft Availability Improvement Program. The process enables the program offices to assess and limit risk, incorporate available support funding, and specifically address where there are effects on availability, such as aircraft in depot. This process also incorporates projecting historical and goal rates in order to leverage scheduled and modernization maintenance. Program offices create plans, known as aircraft availability improvement plans, based on these projections to forecast improvements that can facilitate increased availability and reduction of costs, among other things. The Air Force provides guidance in the form of a template to ensure consistency amongst the plans, which typically must include improvement initiatives with milestone goals. This information includes projected aircraft availability rates for mission capable, units possessed not reported, not mission capable for supply, not mission capable for maintenance, and depot possession. Officials noted that the program office creates an improvement plan each year, regardless of whether it is short of its availability goal, since the plan serves as a forecasting measure. The program is designed to ensure the program offices have plans in place to meet target goals, and the information and milestones laid out in the plans feed into the WSER briefings to senior management. For example: The B-52 plan for fiscal year 2017 discusses the process and milestones for replacing actuator seals for the fleet, the costs of the repair, and the expected benefit to B-52 availability—1.05 percent improvement to the not mission capable supply metric. The C-17 plan for fiscal year 2017 identifies the current and future modifications, timelines for beginning and completion, and the effect on availability. For example, the future replacement of a legacy computer system with a modernized system and display is set to begin in fiscal year 2019 with an estimated completion date of 2026. This replacement is planned to be done concurrently with other maintenance, and to prevent future declines in the C-17’s availability. The F-22 plan for fiscal year 2017 identifies several projects taking place between 2016 and 2021 that are expected to improve availability by almost 2 percent. Further, officials said they are currently working with the Assistant Secretary of the Air Force (Acquisition) to develop an Air Force manual that would make developing an Aircraft Availability Improvement Plan a requirement. This manual will become a supplement to Air Force Instruction 63-101/20-101, according to the officials. Navy program offices for all seven fixed-wing aircraft in our review also have plans for improving availability. According to Navy officials, they started preparing “summary playbooks,” which is the Navy’s term for improvement plans, in late 2015 and started implementing these plans in early 2016 to increase aircraft availability. Officials told us that there was a limitation in funding because of sequestration prior to fiscal year 2017, which hampered their ability to fully implement the playbooks. At a broad level, the Navy’s playbooks include efforts such as maintenance planning, supply support, aircraft material condition and management, and technical data, among other things. These efforts are linked to specific initiatives such as working with the manufacturer and contractors to provide maintenance support, identifying obsolete parts, conducting aircraft fatigue analysis, and updating technical publications, among other things, which have been identified by the program office as ways to improve aircraft availability. Additionally, these playbooks include the extent to which these initiatives are funded, underfunded, or partially funded and the appropriation account that would fund each initiative. The playbooks include the status of each initiative, and some of the playbooks also provide an approximate time frame for implementing each initiative. For example: The playbook for the C-2A has a fatigue analysis initiative focused on analyzing the landing gear to update its design, provide a depot repair manual, and increase its service life, among other things. This initiative is considered funded, is expected to improve aircraft availability, and has an estimated time frame for implementation between fiscal years 2017 and 2021. The playbook for the E-2D contains a maintenance initiative focused on improving the maintenance planning process of the C-2A, E-2C, and E-2D aircraft by completing elements of the product support package, such as training, publications, support equipment, and tools, among others. This initiative is considered partially funded, is expected to improve aircraft availability by decreasing the not mission- capable rates related to maintenance and supply and decreasing maintenance down time, and has an estimated time frame for implementation between fiscal years 2017 through 2019. The playbook for the F/A-18A-D includes a product improvement initiative to conduct a case study to assess the condition of the wiring of the aircraft in the fleet. This initiative is considered funded and is expected to help to sustain aircraft availability. However, there is no time frame for implementing this initiative. The playbook for the F/A-18E-F contains a service life modification initiative focused on extending the service life of the aircraft through modifications. According to officials, this initiative is considered partially funded, is expected to help to sustain aircraft availability, and is expected to help the fleet realize an 80 percent cost avoidance because the Navy will not have to pay the cost to replace these aircraft. Also, this initiative has an estimated time frame for implementation between fiscal years 2018 through 2040. The Departments of the Air Force and Navy spend tens of billions of dollars each year to sustain their fixed-wing aircraft, which need expensive logistics support, including maintenance and repair, to meet goals for availability. The departments spent at least $20 billion annually since 2011 to sustain the 12 aircraft that we examined. 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. These challenges have led to half (6 of 12) of the aircraft in our review experiencing decreasing availability and to the aircraft in general not being able to meet aircraft availability goals. For example, 9 of 12 aircraft did not meet availability goals in fiscal year 2016. These trends are occurring even though the Air Force and Navy regularly review sustainment metrics for the aircraft and are implementing plans for improving aircraft availability. However, DOD’s policy and the Navy’s guidance are not clear on whether the services should have a current sustainment strategy for legacy weapon systems, including fixed-wing aircraft, and on whether the strategies are required to be updated every 5 years. Without clarity about whether the DOD instruction and the Navy guidance apply to legacy systems, program officials will not know whether they are required to have a sustainment strategy or are required to update the plan for their respective fixed-wing aircraft. Furthermore, the program offices, the services, and DOD may not have full visibility of necessary requirements to document program objectives, related risks, and the effectiveness of the program, ultimately jeopardizing the sustainability and affordability of each of the programs. We are making the following two recommendations to DOD: The Secretary of Defense should ensure that the Under Secretary of Defense for Acquisition and Sustainment updates or issues new policy clarifying the requirements for documenting sustainment strategies for legacy weapon systems, including fixed-wing aircraft. (Recommendation 1) The Secretary of the Navy should update or issue new guidance clarifying the requirements for documenting sustainment strategies for legacy weapon systems, including fixed-wing aircraft. (Recommendation 2) We provided a draft of the sensitive report to DOD for review and comment. In written comments that are reproduced in appendix XVI, DOD concurred with our recommendations and noted planned actions to address each recommendation. The Air Force and Navy also provided technical comments, which we incorporated as appropriate. We are sending copies of this report to the appropriate congressional committees; the Secretary of Defense; the Secretaries of the Navy and Air Force; the Commandant of the Marine Corps; the Under Secretary of Defense for Acquisition and Sustainment; and the Director, Defense Logistics Agency. In addition, the report is available at no charge on the GAO website at http://www.gao.gov. If you or your staff have questions about this report, please contact me at merrittz@gao.gov or (202) 512-5257. GAO staff who made key contributions to this report are listed in appendix XVII. Over the past several years, we have conducted work on a number of issues that affect the ability of the Department of Defense (DOD) to sustain its weapon systems. In September 2017, we found that several factors were important to the success of Product Support Managers. These factors included teamwork and collaboration, early implementation of the Product Support Manager position, and organizational support and emphasis on sustainment. We also found that in response to our 2014 recommendations regarding the implementation of the Product Support Manager position, DOD had developed a comprehensive career path and associated guidance to develop, train, and support future Product Support Managers. Additionally, DOD revised guidance to define roles, responsibilities, and reporting relationships between support staff and Product Support Managers. However, DOD was still in the process of implementing our other three recommendations, such as issuing clear, comprehensive, centralized guidance regarding the roles and responsibilities of PSMs and collecting and evaluating information on the effects, if any, that Product Support Managers are having on life-cycle sustainment decisions for their assigned weapon systems. In September 2017, we also found that DOD does not have complete information to identify and manage single-source-of-supply risks. Specifically, some parts are provided by a single source of supply (e.g., one manufacturing facility), and if that single source were no longer able to provide the part, DOD could face challenges in maintaining weapon systems. DOD concurred with our six recommendations focused on improving the completeness of information for single-source-of-supply risks, including issuing department-wide policy that clearly defines requirements of Diminishing Manufacturing Sources and Material Shortages management, and details responsibilities and procedures to be followed to implement the policy. DOD is in the process of taking action to implement these recommendations. In June 2016, we found that the Defense Logistics Agency and the military services have not adopted metrics to measure the accuracy of planning factors, such as the accuracy of part lists, or the costs created by backorders. As a result, depot maintenance may not be efficient or cost-effective, resulting in unnecessary delays in the repair of weapon systems. DOD concurred with our six recommendations to develop metrics to monitor the accuracy of demand planning factors and disruption costs created by the lack of parts at depot maintenance sites and is in the process of taking action to implement these recommendations. For a listing of relevant past GAO work, see the Related GAO Products list at the end of this report. Sustainment: Depot maintenance conducted organically at the designated air logistics complex and contractually for some depot- level repairs at contractor facilities. The B-52 is a long-range, heavy bomber that can perform a variety of missions, including strategic attack, close air support, air interdiction, maritime operations, and offensive counter-air missions. It can carry nuclear or precision-guided conventional ordnance with worldwide precision navigation capability. However, the B-52s are some of the oldest aircraft in the Air Force’s fleet, and will continue to operate until at least 2040 (see fig. 8). Operating and support (O&S) costs for the B-52s have remained relatively steady, generally fluctuating around $1.2 billion–$1.3 billion per year. As a predominantly military-maintained system, most of that O&S cost is related to maintenance and manpower, with depot maintenance and depot-level reparables—direct labor and materials for item repairs, transportation, and storage, among other things—accounting for most of the maintenance cost. Technology Program (2014) is focused on upgrading outdated communications technology. The communications modification requires 7,000 hours of work and is estimated to be complete by 2020. The fleet has active sustainment plans for other components of the aircraft, such as the B-52 Anti-skid Replacement Life Cycle Sustainment Plan (2015), which is estimated to cost over $40 million and be completed by 2019. The B-52 faces sustainment challenges related to its age and, according to officials, replacement parts are difficult to obtain. Several modernization efforts are under way (communications, engines, etc.), and is working with vendors and its own service engineers to identify problem areas and plan ahead so that replacement parts will be available. Depot maintenance on the B-52 is managed by the program office and conducted at Oklahoma City Air Logistics Complex depot. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. The C-17 is a long-range, heavy logistic transport aircraft powered by four F-117 turbofan engines with air-refueling capability that was first manufactured in 1987 (see fig. 10). It is capable of rapid strategic delivery of troops and all types of cargo to main operating bases or to bases in any forward deployment area. The C-17 can perform tactical airlift and airdrop missions and can transport ambulatory patients during aeromedical evacuations, when required. The C-17 can carry virtually all air-transportable equipment. Total operating and support (O&S) costs for the C-17 have decreased from about $5.3 billion in fiscal 2011 to about $4.0 billion in fiscal year 2016. Specifically, unit operations decreased, while maintenance costs have generally increased during this period due to contractor logistics support because the C-17 is a predominantly contractor-managed aircraft. The C-17 Enterprise Life Cycle Management Plan and Life Cycle Sustainment Plan (2014) documents current and future acquisition, sustainment, and integration efforts of the aircraft. It also addresses contractual arrangements and partnership support agreements between Air Force, Boeing, and other service providers for aircraft sustainment. Boeing provides continued sole-source life-cycle support for the C-17 under the terms of the Globemaster Integrated Sustainment Program (2013). Under this program, Boeing is responsible for sustainment, to include material management and depot maintenance support. The C-17 participates in a virtual fleet arrangement, a global network of 43 additional C-17 aircraft, which allows participants total aircraft parts access from any fleet participant worldwide. The C-17 is an aircraft being modified to meet its requirements as well as to address maintenance and supply issues. The Air Force’s actions to mitigate these challenges include processes to increase the service life of the aircraft, allowing managers to quickly hire skilled workers for critical positions, and locating other vendor source for parts. Logistics Complex, and at its facility in San Antonio; landing gear overhaul occurs at Ogden Air Logistics Complex, and engine overhaul occurs at Oklahoma City Air Logistics Complex in partnership with Pratt & Whitney, the original equipment manufacturer on the F-117 turbofan engine. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. Sustainment: Depot maintenance conducted by Northrop Grumman, and field maintenance conducted organically, by the National Guard. The E-8C Joint Surveillance Target Attack Radar System (E-8C) was first manufactured in 1967 (see fig. 12). Its primary mission is to provide theater ground and air commanders with ground surveillance to support attack operations and targeting that contributes to the delay, disruption, and destruction of enemy forces. Total operating and support (O&S) costs for the E-8C have generally increased from about $686 million in fiscal year 2011 to about $734 million in fiscal year 2016. Specifically, maintenance cost has increased partly because of increases in contractor logistics support since the E-8C is maintained by Northrop Grumman. E-8C aircraft were formerly used as commercial airliners and purchased by the Air Force. Therefore, the exact usage of the aircraft was unknown with any degree of specificity. The program office has utilized new analysis conducted by Boeing to develop an improved method of determining and tracking service life for the E-8C aircraft. The new method uses a quantitative analysis capability to identify safety of flight structural concerns, allowing for planning and execution of risk mitigation. The E-8C is an aircraft with significant maintenance and supply issues according to Air Force officials. The Air Force’s actions to mitigate these challenges include updating the Maintenance Plan and the Corrosion Plan for the E-8C (formerly a commercial airframe) to bring them in line with military standards. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. Sustainment: Depot maintenance conducted organically at the designated air logistics complex, and field maintenance conducted organically and by contractors. The F-16 Fighting Falcon is a compact, single-engine, multirole fighter aircraft first manufactured in 1978 (see figure 14). It is highly maneuverable and participates in air-to-air combat and air-to-surface attack. There are four versions of the F-16: A, single-seat model; B, two-seat model with tandem cockpits; C and D, single- and two-seat models, respectively, incorporating newer capabilities. Total operating and support (O&S) cost for the F-16 decreased from about $5 billion in fiscal year 2011 to about $4 billion in fiscal year 2016 because of a 6 percent reduction of inventory. Specifically, maintenance cost has generally decreased during this same period as a result of a decrease in cost of depot maintenance. Sustainment: Performance-based logistics contract with depot maintenance subcontracted to Ogden Air Logistics Complex, Utah, and field maintenance performed organically. and is designed to project air dominance, rapidly and at great distances, and defeat threats. Overall operating and support costs (O&S) for the F-22 have decreased about $248 million overall since fiscal year 2011. Maintenance issues continue to be an area of concern for the aircraft, and these costs increased approximately $255 million from fiscal years 2011 to 2016, due to increases in contractor logistics costs. maintaining a comprehensive diminishing manufacturing sources program and proactively supporting the continued sustainment of component parts of the aircraft through various replacement programs, such as the F-22 Reliability and Maintainability Maturation. This initiative is an ongoing effort to drive continuous improvement in availability. The F-22 faces issues with its low- observable coating and supply funding. Actions to mitigate these challenges include contracting a repair facility to conduct coating reversion repair and securing additional spares funding. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. The AV-8B Harrier (AV-8B) is a Vertical/Short Take-off and Landing attack aircraft first manufactured in 1984 (see fig. 18). The AV-8B has the capability of conducting close air support using conventional weapons for intermediate range intercept and attack missions. The AV-8B is capable of deploying and operating on aircraft carriers and other suitable seagoing platforms, advanced bases, expeditionary airfields, and remote tactical landing sites. Total operating and support (O&S) costs for the AV-8B have decreased from about $815 million in fiscal year 2011 to about $646 million in fiscal year 2016. Specifically, unit-level manpower and operations as well as maintenance costs have decreased partly because the inventory is decreasing as AV-8B squadrons transition to the F-35 Joint Strike Fighter. Average number of flying hours: 4,711 hours per aircraft Operating and support cost: $646 million Depot maintenance activity and squadron locations: AV-8B Program Strategic Sustainment and Warfighting Relevance Plan (2013) addresses strategic sustainment and warfighting requirements to ensure relevance, reliability, safety, and sustainability through five pillars: recruit and retain high-quality people, develop a comprehensive readiness and sustainment plan, meet combatant commander requirements, retain and sustain government and industry agencies to support engineering and logistics requirements, and integrate capabilities to remain tactically relevant and operationally effective. AV-8B is maintained organically at Navy Fleet Readiness Centers under planned maintenance intervals occurring every 1,500 flight hours; supply support is provided organically by Naval Supply Systems Command and Defense Logistics Agency; contractor support services are provided by Boeing. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. Manufacturer: Grumman Corporation (acquired by Northrop Grumman) The C-2A Greyhound Logistics Aircraft (C-2A) is a high-wing, twin-engine monoplane cargo aircraft first manufactured in 1965 (see fig. 20). It is designed to land on aircraft carriers, with a primary mission of providing critical logistics support to Carrier Strike Groups by transporting high-priority cargo, mail, and passengers between carriers and shore bases. The original C-2A aircraft were overhauled to extend their operational life in 1973 and again from 2004 through 2011. Total operating and support (O&S) costs for the C-2A have generally decreased from about $233 million in fiscal year 2011 to about $207 million in fiscal year 2016. Specifically, unit-level manpower, unit operations, and continuing system improvements have decreased, while maintenance costs have increased. landing gear, and avionics system, among others. The Navy will include an appendix for the C-2A when it updates the sustainment strategy for the E 2D for its 5-year update. C-2A completed a service life extension program from 2004 through 2011 to increase flight hours from 10,000 to 15,000 and landings from 16,020 to 36,000, among other things. Aircraft are maintained organically by field maintainers and at Navy Fleet Readiness Centers under a planned maintenance interval cycle with three planned maintenance interval events occurring consecutively every 24 months, and supply support is provided organically by the Naval Supply Systems Command and Defense Logistics Agency. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. The E-2 Hawkeye (E-2C) is the Navy’s all-weather, carrier-based tactical battle management, surface surveillance coordination and airborne early warning, command and control aircraft, with a planned sunset in 2026 when the last E-2D is delivered (see fig. 22). The E-2 is a twin-engine, five- crewmember, high-wing turboprop aircraft with a 24-foot diameter radar rotodome attached to the upper fuselage. Total operating and support (O&S) costs for the E-2 have decreased from about $536 million in fiscal year 2011 to about $345 million in fiscal year 2016. Specifically, unit manpower and maintenance costs have decreased, partly because E-2C inventory is decreasing as E-2C squadrons transition to the E-2D fleet. comprehensive sustainment logistics, engineering programs, and financial resources necessary to ensure continued platform sustainment and attainment of readiness and safety operations. The Navy will include an appendix for the E-2C when it updates the sustainment strategy for the E-2D for its 5-year update. E-2C is maintained organically by field maintainers and at Navy Fleet Readiness Centers under a planned maintenance interval cycle: initial planned maintenance interval is performed by field maintainers at 42 months and the second cycle is performed at a Fleet Readiness Center 46 months after the initial planned maintenance interval. Supply support is provided organically by the Naval Supply Systems Command and Defense Logistics Agency; contractor support services are provided by General Dynamics and Wyle Labs. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. The E-2 Advanced Hawkeye (E-2D) is the newest variant of the E-2 aircraft platform, expecting to reach full operational capability by 2027 (see fig. 24). Using the same configuration as the E-2C, the E-2D aircraft is used for surface-surveillance coordination and airborne early warning, and command control. Its mission is to provide advanced warning of approaching enemy surface units, and cruise missiles and aircraft, among other things. Total operating and support (O&S) costs for the E-2D have increased consistently since fiscal year 2011 to about $125 million in fiscal year 2016. This increase is driven by the addition of aircraft to the inventory as the Navy continues to produce E-2D aircraft through 2026. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. The EA-18G Growler is the fourth major variant of the F/A-18 family of aircraft manufactured in 2007 to replace the EA-6B Prowler (see fig. 26). The EA-18G is the first newly designed electronic warfare aircraft produced in more than 35 years and combines the proven F/A-18 Super Hornet platform with a sophisticated electronic warfare suite. Total O&S costs for the EA-18G have consistently increased from about $334 million in fiscal year 2011 to about $868 million in fiscal year 2016. Specifically, unit manpower and maintenance costs have increased partly because the inventory is increasing, as EA-18Gs are still in production. design, development, and fielding of the aircraft. Some of the key support program elements include developing support equipment and technical data, testing requirements for avionics, and facilities requirements, among others. The Navy is updating this plan and expects to finalize it in 2018. The aircraft are maintained organically at Navy Fleet Readiness Centers under planned maintenance intervals, which typically occur every 72 months. Also, the Navy partners with Boeing to provide wholesale supply and depot repair support for major components, such as the engine. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. The F/A-18A-D Hornet Strike Fighter is a twin-engine, mid-wing, multimission tactical aircraft initially fielded in the 1980s (see fig. 28). In its fighter mode, it is used primarily as a fighter escort and for air defense; in its attack mode, it is used for force projection, interdiction, and air support. Total operating and support (O&S) costs for the F/A-18A-D have decreased consistently from about $3.1 billion in fiscal year 2011 to about $2.4 billion in fiscal year 2016. Specifically, unit manpower, operations, and maintenance costs have decreased, partly because the F/A-18A-Ds are being permanently transitioned out of service to be replaced by the F-35 Joint Strike Fighter.. and financial resources necessary to ensure continued readiness and supportability for the remainder of the aircraft’s service life. The Navy is currently updating this plan and expects to finalize it in 2018. The aircraft are maintained organically at Navy Fleet Readiness Centers under planned maintenance intervals, which typically occur every 48 months for carrier-deploying aircraft, and every 72 months for land-based aircraft. The Navy implemented the High-Flight-Hour program in 2006 to extend the service life from 8,000 to 10,000 flight hours by inspecting and repairing airframes, and replacing major components and parts. The High-Flight-Hour program, along with other factors, has led to maintenance carryover (i.e., into the next fiscal year) due to maintenance events taking longer than planned. In 1999, the Navy entered into a contract with Boeing for engineering support to leverage resources within the technology and industrial base to improve efficiency of the maintenance process and address the maintenance backlog. The F/A-18A-D is operating beyond its planned service life with maintenance and supply issues. The Navy’s actions to mitigate these challenges include extending the service life of the aircraft, allowing maintainers to work overtime to reduce backlog, and cannibalizing parts—moving parts from one aircraft to another. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. The F/A-18E-F Super Hornet was first manufactured in 1998 (see fig. 30). The F/A-18E-F is highly capable across the full mission spectrum: air superiority, fighter escort, reconnaissance, aerial refueling, close air support, air defense suppression, and day/night precision strike. The F/A-18E-F provides aircrew the capability and performance necessary to face 21st century threats. Total operating and support (O&S) costs for the F/A-18E-4 have increased from about $2.2 billion in fiscal year 2011 to about $3.1 billion in fiscal year 2016. Specifically, unit manpower, maintenance, and continuing system support have increased, partly because the inventory is increasing, as the F/A-18E-F is still in production. the Navy is conducting an assessment to determine the number of flight hours the aircraft can safely continue to fly, and then extend the service life of the program through inspections, repairs, and modifications, among other things. The Navy contracted with Boeing to potentially begin these efforts by fiscal year 2018. The F/A-18E-F is a high operational tempo aircraft supporting contingency operations with maintenance and supply issues. The Navy’s actions to mitigate these challenges include plans to extend the service life of the aircraft, training maintainers to transition to vacated positions, and cannibalizing parts—removing parts from one aircraft to another. This report is a public version of a sensitive report that we issued on April 25, 2018. DOD deemed some of the information, such as aircraft availability, not mission capable rates, number of aircraft in depots, and budgeted and executed flight hours to be sensitive (i.e., For Official Use Only). This public report omits the information that DOD deemed to be sensitive. 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. These included two Marine Corps aircraft that are managed by the Department of the Navy. This nongeneralizable sample was selected to ensure a mix of aircraft, including type of aircraft (fighter, bomber, cargo, etc.), age of the aircraft, and size of inventory, and whether the aircraft were sustained organically by the Department of Defense (DOD) or through contract arrangements, such as public-private partnerships or performance-based logistics, among other factors. For the Air Force, we selected five fixed-wing aircraft—the B-52 Stratofortress, C-17 Globemaster III, E-8C Joint Surveillance and Target Attack Radar System (JSTARS), F-16 Fighting Falcon, and F-22 Raptor. For the Navy, including the Marine Corps, we selected seven fixed-wing aircraft—the AV-8B Harrier, C-2A Greyhound Logistics Aircraft, E-2 Hawkeye Early Warning and Control Aircraft, E-2 Advanced Hawkeye Early Warning and Control Aircraft, EA-18G Growler, F/A-18 Hornet Strike Fighter A-D, and F/A-18 Super Hornet E-F. The Marine Corps uses the AV-8B Harrier and also uses a variant of the F/A-18A-D. For the selected aircraft, we obtained and reviewed the aircraft availability, sustainment, and O&S data for accuracy and completeness, interviewed officials regarding their data-collection processes, and reviewed available related policies and procedures associated with the collection of the data. As a result, we found the information to be sufficiently reliable for the purposes of presenting sustainment metrics, such as aircraft availability and O&S costs. status due to maintenance, supply, and both. With respect to O&S costs, we collected and analyzed data from fiscal years 2011 through 2016. We conducted data-reliability assessments for the data provided by the Air Force and the Navy. To do this, we sent data-reliability questionnaires to both departments requesting information on the sources that generated the data. For the Air Force, we conducted data-reliability assessments on the Air Force Total Ownership Cost system and the Logistics Installation and Mission Support system. For the Navy, we conducted data-reliability assessments on the Aviation Management Supply and Readiness Reporting—Type Model Series Integrated Database, the Decision Knowledge Programming for Logistics Analysis and Technical Evaluation system, the Flying Hour Projection System / Cost Adjustment and Visibility Tracking System, and the Visibility and Management of Operating and Support Costs system. We reviewed responses from both departments on these sources as well as documentation—such as guidance, user manuals, and data dictionaries—provided to corroborate questionnaire responses, and interviewed knowledgeable officials to discuss the data. We concluded that the data provided by the Air Force and the Navy were sufficiently reliable for the purposes of reporting condition metrics such as aircraft availability; not mission capable status due to maintenance, supply, and both; depot inductions; budgeted and executed flight hours; and O&S costs for the selected fixed-wing aircraft in our review. To identify the sustainment challenges and mitigation actions for the selected aircraft, we reviewed sustainment metrics data, performance briefings, and other relevant documentation to identify specific challenges for each of the 12 aircraft in our review. We also reviewed ongoing and planned actions to address those challenges. Additionally, we interviewed program officials, depot officials, field maintainers, and squadron personnel to obtain their views on the challenges they face in sustaining the aircraft and the actions they take to mitigate those challenges. In some instances, we visited depots and squadrons to observe aircraft undergoing maintenance, discuss the respective maintenance processes, and discuss challenges and mitigation actions with officials. We then grouped the identified challenges into categories and represented them in a table to demonstrate which aircraft are experiencing specific challenges. To assess the extent to which the Air Force and the Navy have sustainment strategies, regularly review sustainment metrics, and have plans to improve aircraft availability for the selected fixed-wing aircraft, we obtained and analyzed sustainment strategies, performance management frameworks (i.e., sustainment metrics collected and monitored as well as the levels of management review), and improvement plans for each of the selected 12 fixed-wing aircraft. We also identified and reviewed DOD, Air Force, and Navy guidance to analyze the departments’ efforts in sustaining these aircraft and to determine whether these were consistent with federal standards for internal control that deal with management defining objectives in specific terms. Specifically, we reviewed DOD Instruction 5000.02, Operation of the Defense Acquisition System, which provides management principles and mandatory policies for defense acquisition systems such as fixed- wing aircraft. These policies incorporate decision processes and assessing of readiness, which includes the creation of and requirements for a Life-cycle Sustainment Plan. We also reviewed Air Force Instruction 63-101/20-101, Integrated Life Cycle Management, which implements various Air Force and DOD policy directives, including DOD Instruction 5000.02. It establishes the integrated life-cycle management guidelines and procedures for Air Force personnel who develop, review, approve, or manage the systems, subsystems, end-items, services, and activities procured by the Air Force. For the Navy, we reviewed Secretary of the Navy M-5000.2, Department of the Navy Acquisition and Capabilities Guidebook, which provides guidance for the operation of the defense acquisition system and the joint capabilities integration and development system. It also implements DOD Instruction 5000.02 for the Navy and Marine Corps, including guidance on the management and execution of a sustainment strategy. and service guidance. We also reviewed the Air Force’s and the Navy’s performance metric briefings and improvement plans to determine whether the departments regularly reviewed sustainment metrics and had plans aimed at improving aircraft availability. We interviewed DOD, Air Force, and Navy officials knowledgeable about sustainment of these selected fixed-wing aircraft to discuss DOD’s and the departments’ efforts in sustaining these aircraft, including historical information on each aircraft, applicability of policy and guidance for legacy aircraft, and overviews of performance management frameworks identified by the departments to monitor and improve aircraft availability. To develop the fixed-wing aircraft sustainment summary documents (i.e., “Sustainment Quick Looks”) in appendixes II–XIII we obtained historical and current information including background on aircraft capabilities, manufacturer, sustainment strategy, depot maintenance and squadron locations, and key dates in the life cycle of each aircraft (i.e., first manufactured, initial and full operational capability, last production, and planned sunset year). We collected and analyzed the following metrics: aircraft availability, not mission capable maintenance, not mission capable supply, and not mission capable aircraft from fiscal year 2011 through March 2017; the number of aircraft in depots for fiscal years 2011 through 2016; budgeted and executed flight hours from fiscal years 2011 through overall O&S and maintenance costs for fiscal years 2011 through 2016. We compared availability actuals to goals, aircraft in depots to availability trends, and budgeted and executed flight hours to availability trends. We analyzed O&S cost by reviewing its six elements and compared them to availability trends. We also analyzed the subcategories of the maintenance costs element. Through interviews with knowledgeable officials and reviewing documentation, we identified sustainment challenges (i.e., aging, maintenance and supply support) and mitigation actions to address these challenges for each selected fixed-wing aircraft. DOD deemed some of the information, such as aircraft availability, not mission capable status, number of aircraft in depots, and budgeted and executed flight hours, to be sensitive (i.e., For Official Use Only), which must be protected from public disclosure. This public report omits the information that DOD deemed to be sensitive. Additionally, to support our work for each objective we conducted site visits and interviewed officials to discuss data trends and identify specific sustainment challenges such as aging, maintenance, and supply support, among other challenges affecting aircraft availability, and mitigation actions to address these challenges. For the Air Force, we met with the following entities: Headquarters—Secretary of the Air Force, Logistics and Product Support and Deputy Assistant Secretary for Cost and Economics, Air Force Cost Analysis Agency; Materiel Commands—Air Force Materiel Command and Air Force Life Cycle Management Center; Program Offices—B-52 Program Office, C-17 Program Office, E-8C Program Office, F-16 Program Office, and F-22 Program Office; Depots—Tinker Air Force Base at Oklahoma City, Oklahoma (B-52); Robins Air Force Base at Warner Robbins, Georgia (C-17); Northrop Grumman facility at Lake Charles, Louisiana (E-8C); Ogden Air Logistics Center / Hill Air Force Base at Ogden, Utah (F-16 and F-22); and Squadrons—437th Maintenance Group, Joint Base Charleston, South Carolina (C-17); 461st Air Control Wing, Robins Air Force Base Georgia (E-8C); 20th Fighter Wing, Shaw Air Force Base, South Carolina (F-16); and 325th Maintenance Group, Tyndall Air Force Base, Florida (F-22). For the Navy, we met with the following entities: Headquarters—Deputy Assistant Secretary of the Navy— Expeditionary Programs and Logistics Management, Marine Corps Aviation Plans and Policy Branch, and Air Warfare Division; Materiel Commands—Commander, Fleet Readiness Center; Naval Air Systems Command; and Naval Supply Systems Command; Program Offices—Program Manager–Air (PMA)-231 (C-2A, E-2C, and E-2D); PMA- 257 (AV-8B); and PMA-265 (F/A-18A-F, and EA- 18G); Depots—Fleet Readiness Center–East at Cherry Point, North Carolina; Fleet Readiness Center–Mid Atlantic at Naval Air Station Norfolk, Virginia, and Naval Air Station Oceana, Virginia; Squadrons—Marine Corps Air Station Cherry Point, North Carolina; Marine Corps Air Station Miramar, California; Naval Air Station Norfolk, Virginia; and Naval Air Station Oceana, Virginia; and Other—Naval Center for Cost Analysis. The performance audit upon which this report is based was conducted from September 2016 to April 2018 in accordance with generally accepted government auditing standards. Those standards require that we plan and perform the audit to obtain sufficient, appropriate, evidence to provide a reasonable basis for our findings and conclusions based on our audit objectives. We believe that the evidence obtained provides a reasonable basis for our findings and conclusions based on our audit objectives. We subsequently worked with DOD from April 2018 to September 2018 to prepare this unclassified version of the original sensitive report for public release. This public version was also prepared in accordance with these standards. For fiscal year 2016, total operating and support (O&S) costs for the five Air Force fixed-wing aircraft selected in our review were about $12 billion, and the average O&S cost per aircraft across all five fleets was about $96 million, as shown in figure 32. Each of the C-17 and F-16 fleets accounted for about 33 percent of the total O&S cost, and the E-8C’s average cost per aircraft accounted for about 48 percent of the total average cost per aircraft. For fiscal year 2016, total O&S costs for the seven Navy fixed-wing aircraft selected in our review were about $7.7 billion, and the average O&S cost per aircraft across all seven fleets was about $44 million, as shown in figure 33. The F/A-18E-F fleet accounted for about 40 percent of the total O&S cost, and the E-2C’s average cost per aircraft accounted for about 19 percent of the total average cost per aircraft. In addition to the contact named above, John Bumgarner (Assistant Director), Clarine Allen, Ron Aribo, Vincent Buquicchio, Amie Lesser, Richard Powelson, Steven Putansu, Matt Spiers, and Natasha Wilder made key contributions to this report. Defense Supply Chain: DOD Needs Complete Information on Single Sources of Supply to Proactively Manage the Risks. GAO-17-768. Washington, D.C.: September 27, 2017. Weapon Systems Management: Product Support Managers’ Perspectives on Factors Critical to Influencing Sustainment-Related Decisions. GAO-17-744R. Washington, D.C.: September 12, 2017. Defense Acquisitions: Assessments of Selected Weapon Programs. GAO-17-333SP. Washington, D.C.: March 30, 2017. Depot Maintenance: Executed Workload and Maintenance Operations at DOD Depots. GAO-17-82R. Washington, D.C.: February 3, 2017. Defense Inventory: Further Analysis and Enhanced Metrics Could Improve Service Supply and Depot Operations. GAO-16-450. Washington, D.C.: June 9, 2016. Weapon Systems Management: DOD Has Taken Steps to Implement Product Support Managers but Needs to Evaluate Their Effects. GAO-14-326. Washington, D.C.: April 29, 2014.

Answer: 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. 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. 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.