The U.S. Air Force’s X-37B reusable spaceplane returned to Earth May 7 after spending almost two years in space, its longest mission ever.

The Boeing [BA]-built orbital test vehicle landed on a runway at NASA’s Kennedy Space Center in Florida, completing the secretive program’s fourth mission, which lasted 718 days.

“We are incredibly pleased with the performance of the space vehicle and are excited about the data gathered to support the scientific and space communities,” said Lt. Col. Ron Fehlen, the Air Force’s X-37B program manager.

The landing was the vehicle’s first in Florida. The previous three occurred at Vandenberg Air Force Base in California. The program, which is designed to try out reusable flight, re-entry and landing technologies, has now spent a total of 2,085 days on orbit.

The X-37B is slated to begin its fifth mission later in 2017, launching from Cape Canaveral Air Force Station in Florida.

“The program will continue to support technology risk reduction, experimentation and operational concept development for future re-usable space vehicles and serve as a flexible space test platform to conduct various experiments that can be transported to and from the space environment,” an Air Force spokeswoman said.