The rigors of high-speed flight required the development of new metals and special alloys, and some aircraft builders also produced unusual shapes—planes that look like triangles or boomerangs. The strangest shape of all was developed for the F-117A aircraft, to help it elude radar and penetrate heavily defended airspace at night. Lockheed, which began work on the F-117A in the late 1970s, arrayed the flat panels of the plane in such a way that radar energy was deflected or difficult to distinguish. The aircraft, which functions as a bomber, got its first major test during the Gulf War in 1991, and none was lost to enemy fire. But a small payload and high cost raised questions about overall efficacy.

F-117 Stealth Fighter