According to the Air Force, the facility's purpose is as follows: "the testing of technologies and systems training for operations critical to the effectiveness of U.S. military forces and the security of the United States." For years, the secret research and testing efforts conducted there were kept out of view. The 2013 declassification of documents about the U-2 program from the 1950s and 1960s was the first crack in the official curtain of secrecy.
But despite the government's efforts, it's been difficult to keep Area 51's activities completely secret. Here are some of the known projects at Area 51:
- The U-2 Spy Plane: Lockheed worked with the CIA to develop a plane that could fly at a high altitude and spy on other nations. The U-2 could fly at altitudes of 70,000 feet (21,000 meters) and was effective in reconnaissance missions for several years. However, the CIA and Lockheed realized they would soon need more advanced aircraft because the Soviet Union's missile technology was rapidly catching up.
- In 1960, the USSR shot down a U-2, confirming this concern. Engineers designed a plane -- called the Suntan -- to be a successor to the U-2. It could fly at speeds up to Mach 2.5 (almost 2,000 miles or 3,200 kilometers per hour). The Suntan used liquid hydrogen for fuel, which was its ultimate downfall. Engineers decided that it would be too expensive to create a fuel infrastructure to support the Suntan's flights, and the government canceled the project.
- The A-12 OXCART: In the early 1960s, this surveillance aircraft prototype featured a wide, disc-like fuselage made of shiny titanium. A 2009 Los Angeles Times article speculated that the aircraft's appearance and speeds of close to Mach 3 (2,300 miles or 3,700 kilometers per hour) led commercial pilots who encountered it to assume that it was an alien spacecraft.
- The SR-71 Blackbird: This aircraftevolved from the A-12, and became the actual successor to the U-2.These planes could fly at speeds up to Mach 3 and at altitudes of 90,000 feet (27,400 meters).
- Tacit Blue and Have Blue: These two planes were the first successful attempts at creating stealth aircraft. Tacit Blue had an odd, whale-like shape, inspiring onlookers to call it "Shamu." It was designed to fly low over battle operations as a reconnaissance vehicle. Have Blue was a prototype for the F117-A stealth fighter. Have Blue first arrived at Area 51 in 1977. The stealth fighter remained a secret until the Air Force officially unveiled it to the public in 1990.
- The Bird of Prey: A single-seat, gull-wing, experimental aircraft with a radar-evading shape developed from 1992 to 1999, the Bird of Prey pioneered the use of 3-D virtual reality design and assembly processes, and utilized a large, single-piece composite structure. Only one of the aircraft actually was built. In 2002, Boeing, the Bird of Prey's builder, disclosed its existence, because most of its innovations already had become defense industry standards [source: Cole].