McDonnell Douglas C-9 Nightingale

The McDonnell Douglas C-9 is a retired military version of the DC-9 airliner, built as the C-9A Nightingale aeromedical transport for the United States Air Force and as the C-9B Skytrain II for the Navy and Marine Corps. The Air Force identified the need for an aeromedical aircraft in 1966 and ordered the C-9A the following year, with deliveries starting in 1968 and 21 C-9A aircraft received by the end of 1969. They flew medical evacuation, passenger and special missions until 2005. The Navy retired its last C-9B in July 2014, the last two Marine C-9s were retired in April 2017, and a C-9B was still seen as an experimental sensor testbed in 2020.