According to DOD, there were 287 aircraft in the OSA fleet as of May 2017. All OSA aircraft are military variants of commercial aircraft. (See appendix IV for more information and images of these aircraft.) Table 1 lists the number of OSA aircraft by DOD owner/operator and type of usage. A majority of the executive aircraft is located at Joint Base Andrews, Maryland, and a small number are located overseas, as shown in table 2. Thirteen of the 44 executive aircraft are designated as service secretary controlled aircraft. The primary mission for these 13 aircraft is to transport the military departments’ Secretaries, Chiefs of Staff, and other senior officials such as the Undersecretaries and Vice Chiefs of Staff. Service secretary controlled aircraft also support travel for members of congress and for White House support missions, including for cabinet-level officials. In addition, 9 of the 44 executive aircraft are designated for use by the Commanders of the Combatant Commands. As of May 2017, the Army owned and operated 121 of the 243 nonexecutive aircraft. U.S. Africa Command leased one aircraft, and the remaining 121 aircraft belonged to the U.S. Special Operations Command, Marine Corps, Navy, and Air Force, which respectively owned 21, 25, 33, and 42 aircraft. Of the Air Forces’ 42 nonexecutive aircraft, 18 were designated for Defense Intelligence Agency or Defense Security Cooperation Agency support to overseas locations. Multiple officials have responsibilities for approving the use of government aircraft and air travel. Specifically, the Secretaries of the Military Departments, the Chairman of the Joint Chiefs of Staff, and Combatant Commanders review and approve requests within their respective commands. In addition, the Office of the Secretary of Defense Executive Secretary and the Assistant Secretary of Defense for Legislative Affairs prioritize and approve requests within their approval authorities. Table 3 summarizes the responsibilities for approving requests for use of government aircraft. DOD guidance sets clear priorities for the use of its aircraft to support officials in certain positions within the department. Specifically, the guidance lists 26 required DOD users and 35 authorized DOD users of government aircraft who are categorized into four tiers. DOD’s highest priority (tier one) travelers are required to use government aircraft for both official and unofficial travel while tier two travelers are required to use government aircraft only for official travel. The Secretary of Defense prioritizes tier one and tier two officials as travelers that are required to use government aircraft because there is a continuous requirement for secure communications; a threat exists that could endanger lives; or there is a need to satisfy exceptional scheduling requirements that make commercial transportation unacceptable. DOD’s tier three and four travelers are not required to use government aircraft, but are authorized to use the aircraft for official travel when the demands of their travel prevent the use of commercial aircraft. DOD’s aircraft are also used to support employees and members of Congress and White House support missions—a user pool which could total over 550 users. Table 4 lists the required and authorized users of DOD’s aircraft. White House support missions are trips provided by DOD and directed by the President such as travel for cabinet-level officials, the Vice-President, and First Lady. DOD guidance supports travel for members and employees of Congress when approved by the Assistant Secretary of Defense for Legislative Affairs. DOD supports travel for congressional users when the purpose of travel is related to DOD programs or activities. DOD guidance does not support travel for congressional users if a commercial flight is able to meet the users’ departure and arrival requirements within a 24-hour period. However, if the trip includes unusual circumstances, such as a clear and present danger or other compelling operational considerations that make commercial transportation unacceptable, then congressional users may use military aircraft. During calendar years 2014 through 2015, government and military officials took more than 19,000 flights on OSA executive aircraft, and our review of a nongeneralizable, random sample of flight packages from calendar years 2014 and 2015 found that DOD generally followed its guidance for approving use of these aircraft for these selected flights. We analyzed the data for executive flights conducted during calendars years 2014 and 2015, and found that there were a total of 19,752 flights. In both calendar years most of the flights were flown by authorized, but not required users, as shown in Table 5. During calendar years 2014 and 2015, DOD’s four tier one required users accounted for 4 percent of the total executive flights. Its 22 required tier two users accounted for another 27 percent of the total. The remaining 69 percent of the flights were taken by the hundreds of personnel who were authorized, but not required, to use DOD’s executive aircraft. As indicated in table 5, 29 percent of the total executive flight data was categorized in non-specific terms such as “below tier 2 user”. Consequently, it is not possible to provide exact percentages of flight usage for each of the different authorized user categorizes. However, based on the 2014 and 2015 authorized user flight data that was specifically categorized, the following users accounted for at least these percentage of the total flights: tier-three users, 21 percent; tier-four users, 1 percent; White House support mission users, 12 percent; and Congressional delegations, 5 percent. According to DOD officials, most of the non-specific flights were for tier-three-and-four users, but some of the flights were for White House support missions or Congressional delegations. Additional analyses of the calendar year 2014 and 2015 flight data showed that usage rates varied both within and across months and years. For example, in calendar year 2014, the number of daily flights ranged from a low of 2 flights on December 30, 2014, to a high of 70 flights on December 8, 2014. In calendar year 2015, the low ranged from 2 flights on April 5, 2015, to a high of 51 flights on December 18, 2015, and March 31, 2015. During calendar years 2014 and 2015, the executive flights went to over 1,000 locations, and the ten most visited destinations accounted for about 40 percent of those flights. Those locations included Joint Base Andrews in Maryland; Ramstein Air Base in Germany; MacDill Air Force Base in Florida; Scott Air Force Base in Illinois; and Stuttgart Airport in Germany. DOD officials told us that they often see high demand for executive aircraft to support congressional users during congressional recess periods. We found that users in all categories, including congressional, White House support missions, as well as required DOD, and all other authorized users, flew on most days during the 2014 and 2015 two-week spring and four to five-week summer congressional recess periods. However, when we analyzed the total numbers of daily flights, we found that most of days with 40 or more executive flights occurred outside the congressional recess period in calendar year 2014 or 2015, and only one day—during the 2015 spring recess, occurred within those periods. In total, during calendar year 2014, there were 71 days where OSA aircraft flew 40 or more flights, and in 2015 there were 23 days with 40 or more flights. DOD officials told us that they generally prioritize White House support missions and congressional users over tier three or four authorized users. However, at times they are unable to accommodate congressional travelers due to number of participants and distance of travel requirements. DOD officials stated that congressional requests often include larger participant sizes and overseas travel; however, there are a limited number of executive aircraft that can accommodate larger groups and fly long distances. DOD guidance specifies that large executive aircraft (i.e., capable of carrying 15 or more passengers) will be approved only for groups of 5 or more members of Congress. The Air Force has two types of large executive aircraft (C-40s and C-32s). In calendar years 2014 and 2015, we found that 76 percent of the congressional user flights used C-40 executive aircraft, which seat up to 36 passengers and can fly 5,000 nautical miles without refueling. In 2007, DOD established the Executive Airlift Scheduling Activity to facilitate sharing of executive aircraft among the military services and combatant commands when requests exceed capacity. Multiple officials from the services and DOD’s components told us that this sharing approach generally works, and that services usually agree to use their service secretary controlled aircraft to fly officials outside of their service, when asked. Our analysis showed that service secretary controlled aircraft accounted for 13 percent of the executive flights in 2014, and 15 percent of the executive flights in 2015. Table 6 shows that while service secretary controlled aircraft generally flew users from within their associated service, approximately 18 percent of service secretary controlled flights supported users from outside their service. DOD Generally Followed Its Approval Guidance for a Select Set of Executive Flights Reviewed We analyzed flight request packages from a nongeneralizable, random sample of 53 executive flights taken during calendar years 2014 through 2015 and, consistent with a report we issued in 2014, we found that for these select flights DOD generally followed its guidance for approving executive aircraft use. The Secretaries of the Military Departments and Combatant Commanders review and approve OSA aircraft requests within their respective Departments and Commands. The Air Force Deputy Chief of Staff for Operations, Plans and Requirements is also responsible for scheduling congressional and White House support missions. DOD guidance defines a list of procedures for approving the use of OSA. As shown in Figure 1, DOD guidance requires each OSA flight request package to contain specific information, such as the name and rank of traveler, itinerary, cost comparison if needed, and appropriate signatures. Although some packages were missing items, we did not find evidence to suggest the requested flight should have been disapproved. Specifically, 51 of the 53 flight request packages listed the names and titles or ranks of travelers, and 43 of the 53 flight request packages included a signed request.