The first aircraft, a Boeing 747–123 registered N905NA, was originally manufactured for American Airlines. With a decline in air traffic and failure to fill their 747s, American Airlines sold it to NASA. Upon testing, it still wore the visible American cheatlines while testing "Enterprise" in the 1970s. It was acquired in 1974 and initially used for trailing wake vortex research as part of a broader study by NASA Dryden, as well as Shuttle tests involving an F-104 flying in close formation and simulating a release from the 747.