The dimensions of the Hangar:
This hangar could be used anything. It was a topic for a great movie in the 1980's. Nobody knows what it's really used for.
Storage for several or one large alien craft?
A huge elevator which transports the secret plane Aurora, the Black Manta, and others they are testing to an elaborate underground place?
*The Roswell story speaks of the alien bodies and wreckage being taken to a "Hangar 18" at Wright-Patterson AFB in Ohio. All other references including the Federation of American Scientist (FAS.org) has it located here at Area 51.