WASHINGTON (Reuters) -A SpaceX Starship prototype failed in space minutes after launching from Texas on Thursday, forcing airline flights over the Gulf of Mexico to alter course to avoid falling debris and setting back Elon Musk's flagship rocket program.

SpaceX mission control lost contact with a heavily upgraded version of Starship carrying its first test payload of mock satellites, eight minutes after liftoff from its South Texas rocket facilities at 5:38 p.m. EST (2238 GMT).

The last time a Starship upper stage failed was in March last year, but rarely has a SpaceX mishap caused disruptions to air traffic.

At least 20 commercial flights diverted to other airports or altered course to avoid potential debris, based on flight records from tracking website FlightRadar24. The Federal Aviation Administration, which regulates private launch activities, did not immediately return requests for comment.

"We did lose all communications with the ship - that is essentially telling us we had an anomaly with the upper stage," SpaceX Communications Manager Dan Huot said, confirming minutes later that the ship was lost.

The Starship upper stage, two meters (6.56 feet) taller than previous versions, was a "new generation ship with significant upgrades," SpaceX said in a mission description prior to the test. It was due to make a controlled splashdown in the Indian Ocean roughly an hour after its launch from Texas.

The towering Super Heavy booster, meanwhile, returned to its launchpad roughly seven minutes after liftoff, as planned, slowing its descent from space by reigniting its Raptor engines as it hooked itself on giant mechanical arms fixed to a launch tower.