The US's first unmanned re-entry spacecraft has landed at an airfield on the California coast seven months after its launch.
The X-37B's exact purpose remained shrouded in secrecy when it touched-down at Vandenberg Air Force Base on the coast 130 miles northwest 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, the Daily Mail reports.
Jeremy Eggers, 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, according to a NASA statement.
He would not say whether it carried anything in its cargo bay, but insisted 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 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.
Hundreds of millions of dollars have been spent on the X-37 programme, but the current total hasn't been released.
Built by the Boeing Company's Phantom Works, the 11,000-pound craft is 9.5 feet tall and just over 29 feet long, with a wingspan of less than 15 feet. It has two angled tail fins rather than a single vertical stabiliser.