The 1954 GMC XP-21 Firebird I was created in 1953 by the General Motors research team and was eventually referred to as the Firebird I, basically a jet airplane on wheels. The first gas turbine powered vehicle tested in the U.S. the design was incredibly impractical, and featured a bubble topped canopy over a single seat cockpit. This was the first serious attempt by anyone to combine land and air vehicle/components.

This first concept also had a bullet shaped fuselage that was made completely of fiberglass, short wings and a vertical tail fin. The entire vehicle weighed 2,500 lbs and had a 370 hp Whirllfire Turbo Power gas turbine engine which had two speeds, and expelled jet exhaust at around 1,250 °F.

A series of three concept vehicles that were designed by Harley Earl, the GM Firebird was built by General Motors for the 1953, 1956 and 1959 Motorama auto shows. These vehicles were inspired deeply by innovations in fighter aircraft design at the time. These designs were never intended for production, but instead to showcase the extremes in both technology and design that GM was able to achieve.