Photo shows NX21755 after it was rebuilt following a collision with a Lockheed Sirius while landing at Downey. The most obvious change was the fully enclosed cowling it first had was replaced by a more conventional cowling for a radial engine. Went into limited production as the P-66 Vanguard but was soon rejected by the USAAC, the RAF and the Chinese air force which received them. Photo by: Rudy Arnold / Smithsonian Institution

The V-54A, NX21754, was the prototype of the BT-13 Valiant. Soon this apron would be filled with BT-13s and BT-15s, 11,537 of which were built here by a workforce of some 30,000 people. This aircraft was sold to Peru. Photo from: San Diego Air & Space Museum