VIDEO | US Air Force's X-37B lands after 2-year secret mission: All you need to know about space plane

Washington : The US Air Force's X-37B space plane returned to Earth on Sunday after completing a secret space mission that lasted nearly two years. The reusable, unmanned X-37B Orbital Test Vehicle landed at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, an airport used by the US space agency's Space Shuttle for landing until the programme's end in 2011.

Lt. Col. Ron Fehlen, X-37B program manager, said the latest mission set an on-orbit endurance record for the program and marks OTV’s first landing in Florida.

The U.S. Air Force confirmed that its X-37B unmanned mini space shuttle landed at KSC after spending 718 days in orbit. The spacecraft lifted off from Cape Canaveral Air Force Station atop a United Launch Alliance Atlas V rocket on May 20, 2015.

The just-ended mission, known as Orbital Test Vehicle mission 4 (OTV-4), was launched in May 2015 and conducted secret experiments for a total of 718 days while in orbit, Xinhua news agency reported.

It's the fourth and longest-running mission for the X-37B programme, run by the US Air Force's Rapid Capabilities Office. The programme began as a NASA project in 1999 but was later transferred to the Pentagon.

"The landing of OTV-4 marks another success for the X-37B programme and the nation," Lt. Col. Ron Fehlen, X-37B programme manager, was quoted as saying.