X-37B Space Plane Returns From 2-Year Secret Mission

The X-37B space plane returned to Earth on Sunday and landed at the Kennedy Space Center in Florida, ending a two-year classified mission.

While the unmanned plane let many living near the space center know of its arrival with sonic booms, reported Florida Today, the mission of the experimental X-37B Orbital Test Vehicle, as it is formally known, remains a mystery.

The space plane launched from Cape Canaveral Air Force Station on May 20, 2015, for its mission, called OTV-4, and spent 718 days in space.

It was the fourth secret mission for the X-37B space plane, which carries classified payloads on long-duration flights in Earth orbit, said Space.com. The spaceship looks similar to the NASA's now retired space shuttle but smaller, noted the website.

"The landing of OTV-4 marks another success for the X-37B program and the nation," said Air Force Lt. Col. Ron Fehlen, X-37B program manager. "This mission once again set an on-orbit endurance record and marks the vehicle's first landing in the state of Florida."

"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. We are extremely proud of the dedication and hard work by the entire team."

The X-37 program began under NASA in 1999 and was eventually transferred to the U.S. military in 2004 under the Defense Advanced Research Projects Agency (DARPA), noted Space.com. Since then, the X-37 became classified project.

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