Suspended upside down, a titanium A-12 spy-plane prototype is prepped for radar testing at Area 51 in the late 1950s. After a rash of declassifications, details of Cold War workings at the Nevada base, which to this day does not officially exist, are coming to light—including never before released images of an A-12 crash and its cover-up.

(Also see "Revealed: How Area 51 Hid Secret Craft.")

Area 51 was created so that U.S. Cold Warriors with the highest security clearances could pursue cutting-edge aeronautical projects away from prying eyes. During the 1950s and '60s Area 51’s top-secret OXCART program developed the A-12 as the successor to the U-2 spy plane.

Nearly undetectable to radar, the A-12 could fly at 2,200 miles an hour (3,540 kilometers an hour)—fast enough to cross the continental U.S. in 70 minutes. From 90,000 feet (27,400 meters), the plane's cameras could capture foot-long (0.3-meter-long) objects on the ground below.

But pushing the limits came with risks—and a catastrophic 1963 crash of an A-12 based out of Area 51.

A rapid government cover-up removed nearly all public traces of the wrecked A-12—pictured publicly for the first time in this gallery, thanks to the CIA's recent declassification of the images.

(Learn more about Area 51 from the National Geographic Channel.)

—Brian Handwerk

Exclusive Area 51 Pictures: Secret Plane Crash Revealed

In 1963 a prototype rocketed out of the secret base—and never returned. See the crash for the first time, and get closer to the truth about Area 51.