America’s secret space plane is back: The X-37B lands after 780 days in orbit.

The nation’s mysterious space plane is back on the ground after completing another mysterious space mission.

The Air Force’s X-37B Orbital Test Vehicle landed at 3:51 a.m. Sunday at the Shuttle Landing Facility of NASA’s Kennedy Space Center in Cape Canaveral. It spent a record 780 days in orbit.

The X-37B looks like a miniature space shuttle, except it’s an unmanned vehicle that ferries experiments about 150 to 500 miles above the Earth. Boeing built it in 1999 to operate like a space shuttle, riding a rocket into orbit and then gliding to the runway. The X-37B is 29 feet long with a wingspan of nearly 15 feet and has a cargo bay the size of a pickup truck bed.

The X-37B has intrigued space watchers since its first launch in 2010. While the Air Force has released photos of the vehicle, its classified missions are shrouded in mystery. It is used as a test platform for long-term space experiments with military applications that must be brought back to earth. On this mission, the Air Force said the space plane carried experiments from the Air Force Research Laboratory and several small satellites.

The space shuttle fleet was retired in 2011, but the Air Force has at least two X-37Bs.

“The X-37B continues to demonstrate the importance of a reusable spaceplane,” said Secretary of the Air Force Barbara Barrett in a tweet. “Each successive mission advances our nation’s space capabilities.”

Sunday’s landing marks the second time an X-37B has landed at Florida’s Cape Canaveral. The first three flights touched down at Vandenberg Air Force Base in Southern California.

This mission started with the X-37B’s first ride aboard a SpaceX Falcon 9 rocket on Sept. 7, 2017. It is the fifth mission in the program’s history, and broke the old record of 718 days in orbit, according to the Air Force. That is longer than a human crew could spend in space without suffering long-term health problems. By comparison, an astronaut’s mission aboard the International Space Station lasts about six months.

In 2017, the Air Force called the X-37B the latest, most advanced re-entry spacecraft.

“This spacecraft is a key component of the space community,” said Lt. Col. Jonathan Keen, the X-37B program manager. “This milestone demonstrates our commitment to conducting experiments for America’s future space exploration.”

The next X-37B launch is set for 2020 from Cape Canaveral Air Force Station.

Information from Times news services was used in the report.