The APT T-X acquisition strategy poses potential oversight issues for Congress. The addition of a new Major Defense Acquisition Program as the Air Force continues to purchase F-35As and KC-46s and develop the new Long Range Strike Bomber, B-21, will affect the USAF budget requests going forward, and the T-X contract award has already been delayed several times in light of budget issues. Specific to the APT T-X acquisition, Congress may wish to consider the correct number of trainer aircraft and ground-based training systems along with timing of their procurement and fielding. For the purpose of this report, a trainer is defined as an aircraft primarily designed to facilitate aircrew or pilot flight training. Trainer aircraft features include tandem flight controls, simplified cockpit arrangements, and other elements that allow student pilots to operate the aircraft safely. U.S. Air Force trainer aircraft are assigned under the Air Education and Training Command's (AETC's) 19 th Air Force, which includes 19 training locations, 10 regular Air Force wings supported by 6 Guard and Reserve wings, approximately 32,000 personnel, and more than 1,350 aircraft of 29 different models. Currently, the trainer fleet is in use at Joint Base San Antonio-Randolph, Texas; Laughlin Air Force Base (AFB), Texas; Vance AFB, Oklahoma; Columbus AFB, Mississippi; and Sheppard AFB, Texas The current U.S. Air Force (USAF) pilot trainer aircraft fleet consists mainly of the T-6 Texan II, T-1A Jayhawk, and the T-38 Talon. Pilot candidates will generally begin in the T-6, moving to the other aircraft depending on the type of aircraft (fighter, cargo, etc.) to which they will ultimately be assigned. The T-6 Texan II trainer aircraft is a single-engine, two-seat, turboprop aircraft designed to train student pilots in basic flying skills common to both USAF and U.S. Navy (USN) pilots in Joint Primary Pilot Training. A military version of the Beech/Pilatus PC-9 Mk II, the T-6 was originally manufactured by Raytheon Aircraft, later Beechcraft. The USAF acquired the T-6 in May 2000 and began training with it that same year. In 2001, the USAF and USN began using the T-6 as the primary trainer in the Joint Primary Pilot Training program at Moody AFB, GA. The aircraft has tandem seating (one pilot behind the other) with interchangeable instructor/student seating. The aircraft features a pressurized cockpit, an anti-G force system, an advanced avionics package, ejection seats, and fully aerobatic flight controls. The T-6A is the aircraft portion of the Joint Primary Aircraft Training System (JPATS), and is currently in use at Columbus AFB, Mississippi; Vance AFB, Oklahoma; and Laughlin AFB and Sheppard AFB in Texas. The T-1A Jayhawk is a medium-range, twin-engine jet used in the advanced phases of Specialized Undergraduate Pilot Training (SUPT). Students selected to become airlift or tanker aircraft pilots will train in the T-1A after completing Undergraduate Pilot Training. The T-1A was manufactured by Raytheon, later Hawker Beechcraft, and derived from the commercial Beechjet 400A aircraft. The USAF first acquired the jet in 1992 and students began using the aircraft for training in 1993. The main differences between the military aircraft and civilian version are structural enhancements for bird strike resistance and an additional fuel tank. The cockpit is configured to support an instructor pilot and two student pilots. The T-1A is currently used for pilot training at Columbus AFB, Mississippi; Laughlin AFB, Texas; Vance AFB, Oklahoma; and Randolph AFB, Texas; and for combat systems officer training at Naval Air Station Pensacola, FL. The T-38C Talon is a twin-engine, high-altitude, supersonic jet trainer used for Joint Specialized Undergraduate Pilot Training (JSUPT). It is used to train pilots selected to fly fighter and bomber aircraft. Other versions of the T-38 are assigned to Air Combat Command, Air Force Materiel Command, and the National Aeronautics and Space Administration (NASA) in various roles. The T-38 has a history of economy of operations, ease of maintenance, high performance, and exceptional safety. The T-38 was manufactured by Northrop Grumman Corporation and first flew in 1959. Over 1,100 T-38s were delivered to the USAF between 1961 and 1972. The aircraft has swept wings, tricycle landing gear, and a steerable nose wheel. It incorporates a glass cockpit and integrated avionics displays and tandem seating similar to the T-6A. More than 60,000 USAF pilots have trained in the T-38 since entering service. In addition to U.S. forces, the T-38 is in service in Germany, South Korea, Taiwan, and Turkey. Numerous design improvements have been retrofitted into operational T-38s. In 2007, Boeing completed a major avionics suite upgrade to the T-38A/B models, converting 463 T-38s to T-38Cs. Also, Northrop Grumman developed and delivered replacement wing sets to extend the life of the T-38C. In 2015, the USAF embarked on a structural modernization program known as PACER CLASSIC III (see Figure 3 ). The program procures 180 structural upgrade modification kits to ensure the structural integrity of the T-38C aircraft that were at high risk of grounding. The structural work includes replacement of the ejection seat, longerons, landing gear, brakes, flight controls, and canopy, among other structural work. USAF maintainers perform the modifications, extending the aircraft's life to 2029. The USAF's Ogden Air Logistics Complex at Hill AFB, Utah, is charged with executing the modification program. However, the actual modification of the aircraft takes place at Randolph AFB, Texas. The T-38C is used to train USAF, USN, and North Atlantic Treaty Organization (NATO) pilots. In addition, USAF and USN test pilots and flight test engineers are trained in the T-38A. The T-38C is the current trainer used to prepare front-line fighter and bomber pilots to operate all USAF fighters except the F-35. In addition, NASA uses the T-38C to train future astronauts. The USAF identified and documented gaps in its ability to meet advanced pilot training requirements in 2018 and beyond in an October 2009 initial capabilities document (ICD). Within the ICD, the USAF identified 12 shortfalls, out of 18 mission tasks set forth in SUPT and IFF courses, of the T-38C Talon aircraft. (See Appendix C .) Based on the ICD, the USAF commissioned an analysis of alternatives (AOA) in 2011 to determine potential solutions to meet the identified shortfalls in training. In 2014, as a result of a change in the initial operational capability (IOC) date from 2017 to 2023, the USAF published an update to the original 2011 AOA document. The results of the AOA recommended a materiel solution to the issue, and the USAF developed a capabilities development document (CDD) to describe the requirements of the materiel solution, now known as the APT T-X program. The Joint Requirements Oversight Council approved the CDD in October 2015. According to the USAF, the current planned IOC for the APT T-X is 2024 and full operational capability (FOC) in 2034. The stated mission of the APT T-X system is to prepare student pilots to operate fourth- and fifth-generation fighters and bombers. The USAF plans to integrate the APT T-X within the advanced phase of the fighter/bomber track of SUPT as well as IFF. The scope of the acquisition program is to acquire an advanced trainer aircraft and ground-based training system to be used by the Air Education and Training Command (AETC) in the pilot training pipeline. The purpose of the trainer aircraft is to bridge the UPT primary phase in the T-6 Texan and fifth-generation Formal Training Unit (FTU) aircraft. The APT T-X is comprised of multiple systems working together to enable advanced pilot training. The major components include the aircraft, ground-based training systems, virtual training systems, electronic classrooms, aircraft maintainers (personnel), maintenance training systems, and support infrastructure. Figure 5 provides a high-level graphical view of the APT mission and associated architecture capabilities. According to the USAF, the APT T-X system will close the 12 capability gaps identified in the ICD and better prepare student pilots for operations in fifth-generation fighters and bombers. Based on the stated requirements found within the CDD, the APT T-X will provide more effective high-G and high-angle-of-attack training than the T-38C and will more closely resemble fifth-generation operational environments. AETC leaders believe the improved fidelity and aerodynamic modeling required in the Ground-Based Training System (GBTS) will enable better training and allow some tasks to be moved from flight training to the simulators. Also, the more capable aircraft will provide better opportunity to move training from the FTUs into SUPT and IFF, thereby reducing the high cost of flight hours in fifth-generation aircraft normally required to develop experienced pilots.