Top-secret X-37B space plane returns to Earth in dead of night after mysterious 434-day mission, US military reveals

The U.S. government's secretive X-37B space plane has returned to Earth after a 434-day mission in orbit, according to a statement from the U.S. Space Force.

Although the details of the mysterious uncrewed spacecraft's more-than-yearlong mission remain largely classified, the Space Force is touting the recent flight as the start of an "exciting new chapter" in the X-37B program.

"Mission 7 broke new ground by showcasing the X-37B's ability to flexibly accomplish its test and experimentation objectives across orbital regimes," Chief of Space Operations Gen. Chance Saltzman said in the Space Force statement.

In particular, the Space Force noted the space plane's successful completion of several aerobraking maneuvers — a method of utilizing atmospheric drag to lower the plane's orbit while expending minimal amounts of fuel.

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Typically, satellites must use built-in thrusters to change their altitude. By aerobraking, the space plane instead changes the angle of its nose relative to its orbital direction, thus exposing more of its broad underbelly to the atmosphere. This, in turn, generates drag on the plane, gradually slowing it down and lowering its altitude over the course of multiple passes around the planet.

The X-37B launched on Mission 7 from Vandenberg Space Force Base in California on Dec. 29, 2023, riding a SpaceX Falcon Heavy rocket into a highly elliptical orbit around Earth. During the mission, the autonomous space plane also carried out various experiments related to space radiation and "space domain awareness technology," which presumably refers to detecting various objects in orbit, according to the statement. Space Force representatives did not elaborate on what these experiments entailed. The plane returned to Vandenberg in the dark of night on March 7, 2025.

Built by Boeing, the X-37B space plane began as a NASA project before being handed over to the U.S. military in 2004, according to The Aviationist. The mission's primary goal is to advance reusable spacecraft technology, with the craft launching vertically on a rocket, spending months or years in orbit to conduct experiments, and then landing again like a typical airplane. Its longest stint in space so far lasted 909 days, between May 2020 and November 2022. Its shortest flight, in 2010, lasted 224 days.