In 1966, the U.S. Air Force identified a need for an aeromedical transport aircraft and ordered C-9A Nightingale aircraft the following year. Deliveries began in 1968. The U.S. Air Force received 21 C-9A aircraft from 1968 to 1969. . After selecting a modified DC-9 for passenger and cargo transport, the
U.S. Navy ordered its first five C-9Bs, bureau numbers 159030 through 159034. However, since the Air Force was responsible for moving military personnel from place to place in the early 1970s under the Military Airlift Command, this order was canceled. The Navy documented to Congress that their people were being given last seating on Air Force flights. Congress authorized the Navy to fly its own passenger/cargo jets shortly thereafter. The Navy ordered eight aircraft, bureau numbers 159113 through 159120. The first four went to VR-30 at NAS Alameda in California for west coast logistical support while the second four went to VR-1 at Norfolk in Virginia for east coast support. An additional six aircraft, bureau numbers 160046 through 160051 were delivered to the Navy and the Marine Corps in 1976 with the first two aircraft being delivered to the Marine Corps at MCAS Cherry Point, the second two delivered to VR-1 at NAS Norfolk and the last two delivered to VR-30 at NAS Alameda. An additional ten more new and ten used DC-9s were purchased and converted to C-9B for the Navy. The last C-9B to fly for the Navy was retired on 28 June 2014. Many of the Navy's C-9Bs had a higher maximum gross take-off weight of . Auxiliary fuel tanks were installed in the lower cargo hold to augment the aircraft's range to nearly for overseas missions, along with the addition of tail mounted infrared scramblers to counter heat seeking missile threats in hostile environments. ==Operational history==