X-37B Space Plane Returns: 5 Theories About Its Secret Mission

X-37B Space Plane
The X-37B Orbital Test Vehicle on a runway at Vandenberg Air Force Base, in California, in June 2009.
(Image credit: U.S. Air Force)

After spending nearly two years in orbit on a secret mission, the U.S. Air Force's mysterious X-37B space plane landed today (Oct. 17) at Vandenberg Air Force Base in California. The unmanned, reusable vehicle logged an unprecedented 675 days in space, but very little is known about the record-setting flight.

The X-37B, also known as the Orbital Test Vehicle, touched down at the Vandenberg Air Force Base today at 9:24 a.m. local Pacific Time (12:24 p.m. EDT). It was the third in a series of flights that the Air Force has conducted using its two X-37B planes.

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Elizabeth Howell
Live Science Contributor

Elizabeth Howell was staff reporter at Space.com between 2022 and 2024 and a regular contributor to Live Science and Space.com between 2012 and 2022. Elizabeth's reporting includes multiple exclusives with the White House, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?" (ECW Press, 2022) is co-written with astronaut Dave Williams.