An experimental aircraft set a record for hypersonic flight, flying more than three minutes at six times the speed of sound.

The X-51A Waverider was released from a US Air Force B-52 Stratofortress off California yesterday.

Its scramjet engine accelerated it to Mach 6, and it flew under its own power for 200 seconds before losing acceleration. At that point the test was ended.

The Air Force said the previous record for a hypersonic scramjet burn was 12 seconds.

Unlike ordinary ramjets, which use air passing through at subsonic speeds to operate, the X-51 uses a supersonic internal airflow - giving rise to the name scramjet, short for supersonic combustion ramjet.

"We are ecstatic to have accomplished many of the X-51A test points during its first hypersonic mission," said an Air Force Research Lab spokesman.

"We equate this leap in engine technology as equivalent to the post-World War II jump from propeller-driven aircraft to jet engines."

The Waverider was built by Pratt & Whitney Rocketdyne and Boeing.

Joe Vogel, Boeing's director of hypersonics, said, "This is a new world record and sets the foundation for several hypersonic applications, including access to space, reconnaissance, strike, global reach and commercial transportation."

Four X-51A cruisers have been built for the Air Force, and the remaining three will be tested this autumn.