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The term "Area 51" itself has an uncertain origin. It has been speculated that the name derived from atomic energy commission designations, although it appears in various internal CIA documents as well. The site eventually became operationally recognized as a testing ground for various aircraft, including the Lockheed U-2 and its successor, the A-12.
Early flights were often accidental discoveries of new capabilities, with the U-2's first test flight occurring unexpectedly during a high-speed taxi test. As these aircraft came back from their secretive missions, speculation about what exactly was being developed at Area 51 began to mount, particularly concerning exotic technologies and alien vehicles.