The U.S. Space Force’s secretive X-37B space plane is set to launch its eighth mission no earlier than August 21 aboard a Falcon 9 rocket from Kennedy Space Center.

Built by Boeing, the uncrewed, shuttle-shaped spacecraft has completed increasingly long missions since its 2010 debut.

One of the two active X-37Bs recently returned from a 434-day flight, while the other spent a record 908 days in orbit, Ars Technica has reported.

The upcoming launch will likely involve the first of the two vehicles.

Written by B.C. Begley