Boeing Skyfox The Boeing Skyfox was a twin - engined jet trainer aircraft , a highly upgraded development of the Lockheed T - 33 . It was designed as a primary trainer to compete with and replace the Cessna T - 37 Tweety Bird . Besides its primary role as a trainer , the aircraft was envisioned to have other roles as well , including ground attack . The program was started by the Skyfox Corporation in 1983 , and was acquired by Boeing in 1986 . The program included the replacement of the Allison J33 - A - 35 turbojet by two Garrett TFE731 - 3A turbofans . It also included an extensive redesign of the airframe . Only one prototype aircraft was built , and the program was later canceled due to lack of customers . Design and development . Over 6 , 500 Lockheed T - 33 trainers were built , making it one of the most successful jet trainer programs in history . < ref name = " Lockheed TP - 80C / TF - 80C / T - 33A " > Baugher , Joe . " Lockheed TP - 80C / TF - 80C / T - 33A . " " USAF Fighters , " 16 July 1999 . Retrieved : 15 July 2011 . < / ref > However , technology passed the " T - Bird " by , and by the 1980s , it was clear that the world ' s air forces needed a more modern training aircraft . The " Skyfox " was conceived and developed by Russell O ' Quinn . The modification designs were led by T - 33 designer Irvin Culver and a number of other former Lockheed employees formed Flight Concepts Incorporated in 1982 , with the intent of modernizing the T - 33 design . The company ' s name was later changed to Skyfox Corporation . The highly modified and modernized aircraft was expected to cost about half of a new comparable trainer , such as the British Aerospace BAE Hawk and the Dassault / Dornier Alpha Jet . With the design work done , Skyfox purchased 80 surplus T - 33s . The Skyfox was marketed either as a complete converted aircraft from Boeing , or as a conversion kit , with the customer providing the T - 33 airframe . The conversion incorporated about 70 % of the existing T - 33 airframe , but replaced the existing internal single Allison J33 turbojet engine with two Garrett TFE731 - 3A turbofan engines mounted externally . Together , the two TFE731s weighed 17 % less than the single original engine , provided 60 % more thrust on 45 % less fuel . The engine change provided a large internal volume for fuel storage , eliminating the need for the T - 33 ' s tip tanks , but tip mountings were retained to accommodate optional auxiliary fuel tanks if desired . Other modifications included inboard wing leading - edge extensions , the replacement of the tip tanks with winglets , new canopy with one - piece windshield , revised nose geometry to improved visibility from the cockpit and to fair into the T - 33 ' s lateral intakes , new tail surfaces with a mid - set tailplane , although the original wings were retained , and new avionics . Conversion options . The Skyfox was designed to be produced entirely from kits of components . The conversion involved the disassembly , the inspection , and the refurbishment of the T - 33 airframe as necessary , the installation of the kits and reassembly of the airframe in the Skyfox configuration . There were two conversion options : to purchase a complete Skyfox from Boeing or to purchase a conversion kit from Boeing and perform the conversion in the country itself . The standard conversion kit included : Plus control panels for the cockpit In addition to the standard conversion kit described above , Boeing also offered a number of options that could further improve the overall capability of the Skyfox : Operation and support costs . The operating and support costs of the Skyfox were less than that of the T - 33 and could compete with the costs of the Hawk and the Alpha Jet . Structural improvements , avionics upgrades , electrical rewiring , airframe and systems refurbishment , and powerplant modifications resulted in low cost , low maintenance hours and low spare parts consumption . The two TFE371 - 3A turbofans that powered the Skyfox together weighed 17 per cent less than the single J33 - A - 35 turbojet of the T - 33 , while producing 60 percent more thrust and consuming 45 percent less fuel . The TFE371 - 3A turbofan had a ten - fold increase in time between overhauls ( TBO ) compared with the J33 - A - 35 turbojet . The result was a greatly improved maneuverability , range , endurance , payload and the added overwater and hostile terrain safety of the twin powerplant configuration . Potential customers . Portugal . To replace the T - 33A , Portugal signed a letter of intent with the Skyfox Corporation in the middle of the 1980s for 20 conversion kits . The Força Aérea Portuguesa ( FAP ) proposed that Oficinas Gerais de Material Aeronautico ( OGMA ) in Alverca would undertake the conversions , but insufficient orders were obtained from other nations to motivate Boeing to continue with the project . USA . Even the USAF was interested in the Skyfox . It was originally planned to demonstrate the Skyfox at Farnborough International 1986 , but the aircraft was tested at the time by the USAF . Eventually , the USAF did not purchase the Skyfox . Operational history . The first Skyfox converted was an ex - Canadian Forces CT - 133 , the Canadian license - built equivalent of the T - 33 which were formerly a Silver Star 3AT ( Armament Trainer ) . This particular aircraft was produced in 1958 , had construction number T . 33 - 160 and serial number RCAF21160 . < ref name = " CT - 33 / RCAF21160 " > " CT - 33 / RCAF21160 . " " Warbird Registry . " Retrieved : 15 July 2011 . < / ref > It was struck - off charge on 10 November 1970 and was sold through Crown Assets Disposal Corporation to Leroy Penhall / Fighter Imports in 1973 . It was then sold to Murray McCormick Aerial Surveys in 1975 . Its next owner was Consolidated Leasing in 1977 . The Skyfox was sold to the Skyfox Corporation , carrying the U . S . civilian registration number of N221SF , on 14 January 1983 and went to the Flight Test Research in August 1983 . After conversion to the Skyfox configuration it flew its first flight as the Skyfox prototype on 23 August 1983 , nearly 35 . 5 years after the first flight of the T - 33 . Race and test pilot Skip Holm performed the initial flight test at the Mojave Airport , California . The Skyfox prototype was white overall , with black cheat lines , and a very pale blue trim . The Skyfox Corporation was not able to find any buyers for the aircraft , despite its price and capability . However , in 1986 , Boeing Military Aircraft Company saw potential , and purchased the marketing and production rights . Even though Portugal signed a letter of intent for 20 conversion kits , no other nation signed on , and faced with a lack of customers , Boeing cancelled the project . The prototype aircraft remains the only Skyfox built . As of June 2008 , the prototype is parked on the flightline at Rogue Valley International ( MFR ) in Medford , Oregon without engines .