C-9 aircraft acquired by NASA from the U.S. Navy on 9 August 2003 from Whidbey Island NAS, WA. The C-9 is the military version of the McDonnell Douglas DC-9 used for many years by the commercial airlines. The U.S. Navy and U.S. Air Force have utilized the C-9 aircraft in support of passenger transportation, medical evacuation and special missions.

The primary mission of the NASA C-9 is to provide NASA and government microgravity researchers the platform to perform their research in a reduced gravity environment. The aircraft is also utilized for Heavy Aircraft Training (HAT) for astronaut pilots, support the movement of the shuttle from landing sites in California and New Mexico back to Kennedy Space Center, Trans-Atlantic Landing support and the Emergency Mission Control Move mission.