OSA missions support the movement of a limited number of high-priority passengers and cargo with time, place, or mission-sensitive requirements. DODs OSA aircraft are variants of commercial aircraft. OSA aircraft are categorized as either executive (used to transport DOD, congressional, and cabinet officials) or non-executive (used to fulfill wartime or contingency needs). As of May 2017, DOD had 287 OSA aircraft44 executive and 243 non-executiveabout 6 percent of DODs airlift/cargo/utility aircraft. House Report 114-537 and Senate Report 114-255 included provisions for GAO to review the use and size of the OSA fleet. This report examines the extent to which DOD (1) used OSA executive aircraft in 2014 and 2015, and if this usage complied with guidance; and (2) has a process to validate its OSA fleet size. GAO reviewed DOD guidance for approving the use of OSA aircraft, analyzed the most current executive aircraft flight data availablecalendar years 2014 and 2015and compared the approval documentation from a sample of those flights to DODs guidance. GAO also reviewed documentation and interviewed officials to assess DODs OSA validation process and results.