The NASA M2-F1 was a lightweight, unpowered prototype aircraft, developed to flight test the wingless lifting body concept. It looked like a "flying bathtub," and was designated the M2-F1, the "M" referring to "manned" and "F" referring to "flight" version. In 1962, NASA Dryden management approved a program to build a lightweight, unpowered lifting body prototype. It featured a plywood shell placed over a tubular steel frame crafted at Dryden. Construction was completed in 1963.