The Justice League Hangar was used by the Justice League of America as a place to store their aircraft and spacecraft, such as the invisible jet, Batcopter and probably even the Supermobile. A runway was located right outside the hangar for the purpose of takeoff and landing of the invisible jet.
When Batman and Robin were on their way to Egypt for a Justice League assignment, he took off in his Batcopter at the Justice League Hangar. Wonder Woman too, used her airplane to head off to England, using the Justice League Runway for liftoff.
Justice League Runway
When Marvin White and Wendy Harris were inside the Hall of Justice trying to figure out a way to locate the missing Justice League, that were kidnapped by Doctor Hiram Gulliver, they decided to get into the Amazon Princess's jet and see if they could fly it to her using their own head. This didn't work, because they don't have telepathic powers. Nevertheless Wonder Woman summoned the jet herself, and brought them along for the ride.
The exact location of the Justice League Hangar wasn't entirely clear, but presumably it was very close to the Hall of Justice. This is implied by the fact that Marvin White and Wendy Harris seemed to go there on foot in a fairly short period of time, although this is merely conjecture.
It should also be noted that the hangar seemed to be located in an area with no other buildings around, possibly a rural area, which seems strange, since the Hall at that time was located in Downtown Gotham City.
- The name of this hangar is just conjecture based upon other similar names of things and places that were owned by the JLA, such as the Justice League Arsenal, Justice League Laboratory and Justice League spectral analyzer.