Spy plane? Weapons carrier? Troop transport? Nobody was quite sure what the unmanned X-37B was doing while it orbited the Earth for more than a year, and the speculation continued after it touched down at Vandenberg Air Force Base Saturday, 130 miles north of Los Angeles.

“I don't think this thing has a mission that would go beyond bewildering the Chinese,” national security analyst John Pike, who founded GlobalSecurity.org, told The Guardian.

“It is the sum of all fears,” Pike said. “They don't know what it is and they have to hedge against everything it might be, even though I think it's nothing. It's part of a strategic deception program. It looks good; it sounds neat and everything. I assume they put little space experiments, some damn little camera in there. I'm sure the payload bay is chock full of little goodies they're flying on an opportunity basis. But, if the thing was actually useful for some national purpose, it would have flown a long time ago because somebody would have been hot to trot.”

The super-secret plane launched from Cape Canaveral Air Force Station in Florida in March 2011 and for awhile its orbital path was nearly identical to that of China’s spacelab, Tiangong-1. The X-37B, built by Boeing’s Phantom Works group, looks like a chubby American space shuttle, which is no longer being flown, but is less than half the size.

Joan Johnson-Freese, professor of national security affairs at the Naval War College, votes for the eye-in-sky theory because it could give the U.S. a presence over conflict regions faster than a satellite. But Yousaf Butt, a nuclear physicist and scientific consultant for the Federation of American Scientists, thinks the program, which originated in 1999 and has changed hands several times—bouncing from NASA to the Pentagon’s DARPA unit before landing at the secretive Air Force Rapid Capabilities Office—has a less mysterious reason for being.

“I believe one of the reasons that the mission is still around is institutional inertia,” Butt said, arguing that the capabilities of the X-37B could be done more cheaply with a disposable spacecraft.

-Ken Broder

To Learn More:

Unmanned Air Force Space Plane Lands in Calif. (by Alicia Chang, Associated Press)

Mysterious U.S. Space Spy Plane Probably Tracking China (by Noel Brinkerhoff, AllGov)

Secret Air Force Space Plane Touches Down After Mystery Mission (by Damon Poeter, PC Magazine)

Air Force Plans to Land Its Mysterious Unmanned Space Plane in June (by Brian Braiker, The Guardian)