turboprop-powered aircraft. Operationally, the HU-25 played a key role in the service's actitives in search and rescue, counter drug missions; it had also been a critical asset deployed during the 1991 Gulf War. Initial models of the HU-25 were delivered to the HU-25A standard; a number were later modified to become HU-25Bs, which were equipped with sensors capable of detecting oil spills and other environmental pollutants. Further numbers were re-configured to the HU-25C standard, for improved performance in the drug interdiction mission; when equipped with newer AN/APG-66(V)2 and AN/APS-143B(V)3 radar systems, these became the HU-25C+ and HU-25D respectively. On 26 September 2014, following 32 years of service, the last operational HU-25 Falcon, the only jet ever to be a part of the air fleet of the US Coast Guard, was retired. The high-speed capability it provided will be lost with the type's retirement due to its replacements being considerably slower aircraft. Aerial testbeds In 1988 the United States Coast Guard tested a Falcon 20C (tail-number N200GT) using Garrett TFE1042 afterburners. This required adding a titanium heat shield to the tail due to the engine mount position. In 1990, the United States Air Force acquired N20NY (cn 61), a Falcon 20C, for use as a testbed at MIT Lincoln Laboratory. In 2006, the USAF also acquired Coast Guard HU-25A 2125, registered as N448TB (cn 439), for use at Lincoln Laboratory. Sometime in the mid to late 2000s, N20NY was retired and donated to a local community college, with N448TB also being retired and donated to the same school in June, 2022. In 2011, NASA acquired a former Coast Guard HU-25C for use in Operation IceBridge. The aircraft, based at NASA's Langley Research Center in Hampton, Virginia, is equipped with a scanning laser altimeter to collect data on Arctic surface topography. During November 2012, a Falcon 20 became the first civil jet in the world to fly on 100 per cent biofuel when it performed a test flight for Canada's National Research Council. Variants Mystère/Falcon 20 Prototype, one built. F-WLKB, initially powered by two Pratt & Whitney JT12A-8 turbojet engines. Now stored at Musée Air et Espace Aéroport Paris – Le Bourget. Mystère/Falcon 20C Initial production version. known in the US as the Falcon 20 Basic. Powered by the CF700-2C engines. Falcon 20CC (s/n 073) One aircraft similar to the Falcon 20C, equipped with low-pressure tyres (Gravel runway modification, with reinforced belly,