The A-10 is a single seat fixed-wing platform specifically designed for close air support and defeating enemy armor. According to the Air Force, this fourth generation fighter achieved its initial operational capability in 1977, but the aircraft has received many upgrades since that time, including a major modernization in 2007. The Air Force describes the A- 10 as a highly accurate and survivable weapons-delivery platform with excellent maneuverability at low air speeds and altitude, a wide combat radius, and extended loiter times. Figure 1 shows a picture of an A-10. As of April 2016, the Air Force A-10 inventory includes 283 aircraft stationed across the United States and also in South Korea, as shown in figure 2. The Air Force assigns three primary missions and two secondary missions to the A-10, which are described in table 1. The A-10 is one of a number of DOD aircraft—both manned and unmanned—that conduct the CAS mission. Besides the A-10, the Air Force currently has two other fighter aircraft that conduct the CAS mission (F-16 and F-15E) and plans to use the F-35 for this mission in the future. The Air Force also uses bombers (B-1, B-52), special operations aircraft (AC-130), and remotely-piloted aircraft (MQ-1, MQ-9) to conduct CAS. Other DOD assets used for CAS include the F/A-18 (Navy/Marine Corps), AV-8 (Marine Corps), AH-1 (Marine Corps), and AH-64 (Army). Figure 3 includes examples of CAS-capable aircraft in the Air Force and other services. Joint Terminal Attack Controllers provide ground commanders with recommendations on the use of CAS and its integration with ground operations. According to Joint Doctrine, Joint Terminal Attack Controllers are qualified (certified) servicemembers who, from a forward position, direct the action of combat aircraft engaged in CAS and other offensive air operations. FAC(A)s are also qualified to exercise control of aircraft engaged in CAS, but FAC(A)s exercise control from the air while Joint Terminal Attack Controllers typically exercise control from ground positions. In short, both are responsible for ensuring that aircraft strike the target accurately while avoiding hitting friendly troops. DOD and partner nations have Memorandums of Agreement that standardize Joint Terminal Attack Controller and FAC(A) certification and qualification requirements, including identifying minimum training and performance standards. Joint Terminal Attack Controllers and FAC(A)s are the only personnel authorized to control the maneuver of, or grant weapons release clearance to, attacking aircraft. The Air Force and DOD do not have needed information on the full implications of A-10 divestment, including the gaps that could be created by divestment and options for mitigating any potential gaps. Divestment decisions can have far-reaching consequences and should be based on quality information. The Air Force’s recent proposal to postpone full A-10 divestment until 2022 mitigates some near-term capacity gaps, but divestment may still create capacity gaps and gaps in the service’s ability to conduct missions currently carried out by the A-10. Moreover, the Air Force has not yet clearly identified gaps and resulting risks that could be created by A-10 divestment, so it is not well-positioned to determine appropriate mitigation strategies. Further, DOD may face similar decisions to divest other weapon systems before the end of their service lives in the future and does not have guidance to ensure that the services and the department overall are collecting quality information to inform these decisions. Because they can have far-reaching cost and operational consequences, major divestment decisions, like the original decisions to invest in platforms, should be based on quality information. With regard to DOD’s divestment actions that would affect military capabilities, this quality information should, among other things, clearly identify any gaps created by the action and strategies for mitigating any gaps that result from the action. The Air Force has numerous policy documents to guide investment decisions; by contrast, it does not have guidance identifying the factors it must consider before choosing to divest a major weapon system before the end of its expected service life. Although the Air Force lacks specific guidance to identify the factors it must consider before choosing to divest a major weapon system, the Air Force has guidance that recognizes that divestment decisions, like investment decisions, are actions that can have major financial and non-financial consequences for an organization and so should be carefully considered. Similarly, we were not able to find DOD guidance specifically identifying such factors. However, DOD guidance and GAO knowledge-based criteria identify key factors that, while developed for investment decisions, are applicable to making divestment decisions. One key factor is having clear requirements, which (1) provide a baseline to identify gaps and associated risks, and (2) inform decisions on how best to address the gaps. The Navy has also recognized the similarities between investment and divestment decisions, and it has issued guidance requiring that senior Navy leaders and Congress be provided specific information to support proposals to divest a vessel before the end of its expected service life. Specifically, these proposals must describe the reason for the divestment, identify any resulting capability gaps, and recommend strategies for mitigating gaps. The Air Force’s current A-10 divestment proposal delays loss in fighter capacity that would have occurred under prior proposals. If implemented, the current proposal would result in the complete divestment of the A-10 by 2022, 3 years later than proposed in the fiscal years 2015 and 2016 budget requests. The Air Force 2014 budget request anticipated retaining all 283 A-10s through at least 2035. However, Air Force leaders have recently testified that the service must start divesting the A-10 fleet after fiscal year 2017 because, without an increase in personnel and associated funding, the Air Force does not have the manpower needed to support both the A-10 and F-35 fleets. Figure 4 provides a comparison of the 2015, 2016, and 2017 divestment proposals. Changes in the current operational environment—specifically the rise of the Islamic State of Iraq and the Levant (ISIL) and Russia’s provocations—led to increased fighter aircraft demands and also affected the decision to temporarily defer A-10 divestment, according to the Air Force. This decision was made in consultation with the combatant commanders, according to Air Force testimony. Since the Air Force originally proposed divesting its A-10s, units have deployed to U.S. European Command (EUCOM), U.S. Central Command (CENTCOM), and U.S. Pacific Command. The A-10 brings useful and unique capabilities to the battlefield, according to officials from the commands. The Secretary of Defense noted that the A-10 has been devastating ISIL. Figure 5 shows A-10s returning from a deployment to EUCOM. Although the 2017 A-10 divestment proposal provides more near-term fighter capacity than the two prior proposals, implementation of this latest divestment proposal could still lead to near-term capacity gaps. According to a DOD summary of its fiscal year 2017 budget proposal, the Air Force plans to replace A-10 squadrons one-for-one with F-35 squadrons in order to mitigate the drop in fighter capacity projected under the original A-10 divestment proposal. However, Air Force documentation reveals that the loss of A-10 squadrons will outpace the F-35 squadron gain, with eight A-10 squadrons divested by the end of the 5-year budget plan but only six F-35 squadrons stood up. North Korea remains one of the most challenging security problems for the United States and its allies and partners in the region, according to DOD. DOD reports that North Korea’s large, forward-positioned military can initiate an attack against South Korea with little or no warning. In April 2015, the U.S. Forces Korea commander testified that having very little warning of a provocation was the command’s top concern. In response to questions, the commander also stated that loss of the A-10 would create a gap, primarily in the ability to defeat the North Korean armor threat. He also testified that he had been assured that, should the A-10 unit based in South Korea be divested, it would be replaced by another squadron in South Korea. However, the current Air Force proposal would divest the A-10 squadron in South Korea in fiscal year 2019 without replacement. We found that the full extent to which the divestment proposals create capacity gaps and increase risk is difficult to determine, because DOD does not have a clearly established Air Force fighter aircraft capacity requirement. However, all three A-10 divestment proposals would contribute to a decline in Air Force fighter capacity, when compared to the Air Force’s fiscal year 2014 budget plans, which called for the Air Force to maintain its A-10s through 2035. In March 2016, the Air Force began a major force structure review that will include an examination of its fighter capacity requirements, according to Air Force officials. Until it has such a baseline, the Air Force cannot determine the full extent of capacity gaps and associated risks it will incur under its current A-10 divestment proposal and the effectiveness or necessity of any mitigation strategies. Figure 6 shows the Air Force’s planned fighter and bomber inventories from 2017 through 2046. The Air Force has not comprehensively assessed potential mission capability gaps caused by A-10 divestment or the effects of divestment on its ability to support Joint Terminal Attack Controller training.