, 1982 Throughout the 1960s and 1970s the C-1 Trader carried mail and supplies to
aircraft carriers on station in the Pacific Ocean during the
Vietnam War and also served as a trainer for all-weather carrier operations. Over its production life 87 C-1 Traders were built, of which four were converted into
EC-1A Tracer electronic countermeasures aircraft. The last C-1 was retired from USN service in 1988; it was the second-to-last
radial engine aircraft in US military service, preceding the
Convair C-131 which was retired in 1990. As of 2010, approximately ten were still airworthy in civil hands, operating as
warbirds. In 1956 the US Marine Corps Test Unit Number 1 (MCTU #1) tested the concept of using the TF-1 variant as a vehicle for inserting
reconnaissance teams behind enemy lines. "On 9 July 1956 MCTU Recon Marines became the first to parachute from a TF-1. Less than three weeks later, four recon parachutists launched from the
USS Bennington, which was at sea, and jumped on a desert drop zone near
El Centro California, some inland. For the first time in Marine Corps and Naval Aviation history, the technique of introducing recon personnel off a carrier sea base to an inland objective had successfully been tested." In August 2010,
Brazilian Naval Aviation announced that it would buy and modernize eight C-1 airframes to serve in carrier onboard delivery and
aerial refueling roles for use on its aircraft carrier
São Paulo. In 2011 contract was signed with Marsh Aviation to convert four ex-US Navy C-1A Trader airframes into KC-2 Turbo Traders. The first KC-2 prototype flight was expected for November 2017 and the delivery of the first operational aircraft was scheduled for December 2018; in 2014 the contract was reaffirmed, ==Variants==