The Guardian report:
The US government “secretly acquired” Soviet aircraft during the Cold War and tested them at Area 51, according to documents released Tuesday that shed light on the once-classified and long speculated base deep in the Nevada desert.
The CIA in August confirmed the existence of Area 51 when it released declassified documents through a Freedom of Information Act request by George Washington University’s National Security Archive.
The initial documents show that Area 51 was used to test the US government’s aerial programs.