Loud boom heard Sunday was space plane returning

BREVARD COUNTY, Fla. – People who live along the coast may have heard a loud boom Sunday. The U.S. Air Force says its secretive X-37B unmanned space plane returned to the Kennedy Space Center after nearly two years in orbit.

The 29-foot-long place is about a quarter size of a space shuttle.

"The X-37B continues to demonstrate the importance of a reusable space plane," Secretary of the Air Force Barbara Barrett said in a statement. "Each successive mission advances our nation's space capabilities."

The X-37B is considered the Air Force's top premier reusable, unmanned spacecraft. Its mission experiments are typically kept top secret but have a focus on Air Force Research Laboratory experiments along with providing a lift into orbit for small satellites. 

The X-37B's next flight will launch from Cape Canaveral sometime in 2020.