The X-37B’s exact purpose remained shrouded in secrecy when it touched-down at at Vandenberg Air Force Base on the California coast 130 miles north west of Los Angeles.
It was launched by an Atlas 5 rocket from Cape Canaveral, Florida, on April 22, with a maximum mission duration of 270 days and is suspected of being an advanced spy plane.
Also known as the Orbital Test Vehicle, the Boeing-built spacecraft was originally a NASA project before being taken over by the military.
Jeremy Eggers, a spokesman for Vandenberg Air Force Base, described the successful landing as ‘very exciting’ and said the X-37B was due to return to space next year.
He said would not say whether it carried anything in its cargo bay, but insists the primary purpose of the mission was to test the craft itself.
Theories have abounded following the secretive launch, with some experts suggesting the spacecraft is America’s attempt at gaining the military dominance of space.
‘We are very pleased that the program completed all the on-orbit objectives for the first mission,’ programme manager Lt. Col. Troy Giese said in a statement.