But the overview isn’t totally bereft of details. At more than 36,000 square feet, the shelter is definitely big—although not the Pentagon’s largest hangar. In 2005, contractors built a 51,000-square-foot hangar at Andersen Air Force Base in Guam.

That maintenance structure—known as Hangar 1—had to be big so that the Air Force’s massive B-2 and B-52 bombers could fit inside during typhoons.

The Guam hangar can also hold smaller planes such as the F-22 stealth fighter, contractor Burns & McDonnell states on its Website. Sometime in the last six years, a top-secret RQ-170 Sentinel drone also posed near the massive building.

But we probably shouldn’t read too much into the secret hangar’s size. “As to hangar size … it’s all going to be aircraft specific,” explains Brian Laslie, an Air Force historian, referring to aircraft shelters in general. “It’s more of a maintenance requirement than anything else.”

The request doesn’t mention a new runway, which means the structure will likely end up at an existing air base. “That would have to be Florida,” says John Pike, director of the military information website GlobalSecurity.org. “There’s where SOCOM lives.”

The Pentagon’s commando headquarters is at MacDill Air Force Base near Tampa.

Another possibility is Tonopah Test Range in Nevada. Most observors associate that secure facility with secretive aircraft such as the stealthy Sentinel and the old F-117 stealth fighter.

If Congress approves the funds and Special Operations Command builds the new hangar, commandos could use the structure to help out with “overseas contingency operations, as required,” according to the project description.

“It could be Reapers,” Pike posits. The Air Force wants to buy 29 more of these deadly drones, according to the recent budget request.

Air Combat Command—which controls the bulk of the Air Force’s fighter jets, spy planes and drones—wants to acquire as many as 400 MQ-9s, according a recent review of the program. Aerial commandos could be in the process of consolidating their own smaller fleet of the propeller-driven unmanned aerial vehicles.

“Or it could be one of the stealthy UAVs we don’t know about,” Pike notes.

In June 2014, the Air Force admitted it was working on a new, super-secret pilotless spy plane called the RQ-180. Then the following January, the Pentagon announced plans for another experimental aircraft.

“The Defense Advanced Research Projects Agency initially will lead the program,” Under Secretary of Defense for Acquisition, Technology and Logistics Frank Kendall told legislators on Jan. 28.