Washington, Dec 21 (IANS): The unmanned Boeing Starliner spacecraft, launched on Friday, didn't reach the planned orbit, but SpaceX CEO Elon Musk sent his best wishes to the mission.

"Orbit is hard. Best wishes for landing & swift recovery to next mission," Musk tweeted after NASA revealed that Starliner was in an unplanned, but stable orbit.

Boeing's passenger spacecraft was launched on its first unmanned flight test to the International Space Station (ISS) atop a United Launch Alliance (ULA) Atlas V rocket from Cape Canaveral Air Force Station in Florida, but the mission didn't go as planned.

"Starliner didn't reach the planned orbit and will not dock to the space station. Teams worked quickly to ensure the spacecraft was in a stable orbit and preserved enough fuel for a landing opportunity," NASA said.

"Boeing, in coordination with NASA and the US Army, is working to return Starliner to land at White Sands, New Mexico, on Sunday, December 22," the US space agency said.

Earlier this year, the SpaceX's Crew Dragon capsule completed historic unmanned flight test to the space station.

NASA selected SpaceX and Boeing to create integrated spacecraft, rockets and associated systems to carry astronauts on NASA missions in September 2014.