This dark-painted fighter, based on the airframe of the Bell P-63 Kingcobra, represents the Bell L-39 — a rare experimental testbed built in 1946 with modified swept outer wing panels. Flown by Bell Aircraft and NACA test pilots, the L-39 gathered vital low-speed aerodynamic data on swept-wing design, research that helped pave the way for America's first generation of swept-wing jet aircraft. Project: 218475