A top secret government space plane is the next launch scheduled for United Launch Alliance's Atlas V rocket.

The X-37B spacecraft is set to launch on top of the rocket, from Space Launch Complex 41 at the Cape Canaveral Air Force Station.

The launch was originally set for May 6, but is now delayed until no earlier than May 20.

Not a lot is known about this unmanned vehicle for the U.S. Air Force but some space experts suspect it spies on behalf of the U.S. government.

Last year, operations of the X37-B were moved from California to Florida's Kennedy Space Center.