WASHINGTON — The U.S.  Air Force’s classified spaceplane, the X-37B, is probably not landing today despite earlier rumors that it would.

“The X-37 is still on-orbit. The program is conducting a regularly scheduled exercise this week,” said a statement from Air Force spokeswoman Capt. Annmarie Annicelli.

Several websites reported Tuesday morning that the craft was maneuvering in possible preparation for a landing, but it appears instead to be taking part in a planned exercise.

This is the fourth mission for the top-secret, Boeing-built spaceplane. It launched May 20, 2015. There are actually two spacecraft, according to the Air Force, each about 29 feet long and 9 feet high, with a 14-foot wingspan, and clocking in at 11,000 pounds each.

The two spacecraft have alternated flying missions since the first one launched in April 2010.

According to previous information provided by the Air Force, the spaceplanes are testing out “advanced guidance, navigation and control, thermal protection systems, avionics, high temperature structures and seals, conformal reusable insulation, lightweight electromechanical flight systems, advanced propulsion systems, and autonomous orbital flight, reentry, and landing.”

Phillip Swarts is the military space reporter for SpaceNews. He previously covered space and advanced technology for Air Force Times, the Justice Department for The Washington Times, and investigative journalism for the Washington Guardian;...