SpaceX launched its Falcon Heavy rocket on a classified mission for the National Reconnaissance Office (NRO), marking the first time the U.S. spy satellite agency has used the powerful rocket.

The NROL-97 mission launched from NASA’s Kennedy Space Center in Florida late October 1 and carried a classified payload whose exact purpose and destination remain undisclosed. 

The Falcon Heavy uses three Falcon 9-derived boosters and has now completed its 14th flight, with the two side boosters successfully landing back at Cape Canaveral. 

The NRO had previously launched 22 missions aboard Falcon 9 rockets, but this was its first Falcon Heavy mission and the first NRO payload procured under the newer National Security Space Launch contract, Spaceflight Now has reported.

Because NRO missions are classified, little is known publicly about NROL-97, although the use of Falcon Heavy indicates the mission required the rocket’s greater lifting capability or a trajectory beyond typical low-Earth orbit.