The next launch of the U.S. Air Force’s X-37B unmanned reusable spaceplane will occur “no earlier than September,” launch vehicle provider SpaceX said Aug. 14.

The Air Force had previously indicated that the launch would occur “no earlier than August,” but it cautioned that the launch date was “still in the process of being manifested on the range schedule.”

The Air Force's X-37B spaceplane lands at NASA's Kennedy Space Center in Florida on May 7, 2017. (Photo courtesy of Air Force)
The Air Force’s X-37B spaceplane lands at NASA’s Kennedy Space Center in Florida on May 7, 2017. (Photo courtesy of Air Force)

The mission, the fifth for the Boeing [BA]-built Orbital Test Vehicle, will launch from Launch Complex 39A at NASA’s Kennedy Space Center in Florida. It will be the first to use SpaceX’s Falcon 9 rocket. Each of the previous four missions rode aboard a United Launch Alliance (ULA) Atlas 5 rocket.

The X-37B’s longest trip ended in May after almost two years in space. The program is designed to try out reusable flight, re-entry and landing technologies.