An experimental hypersonic plane has broken the world speed record by flying at seven times the speed of sound, says US space agency Nasa.
The plane was dropped from the wing of a B-52 bomber
The unpiloted X-43A aircraft used a scramjet engine that could one day usher in a new generation of space shuttle propulsion systems.
It flew for 10 seconds on its own power over California, then glided for six minutes before falling into the ocean.
"Everything went according to plan," said Nasa spokeswoman Leslie Williams.
"I actually thought it was the most beautiful thing I've ever seen. We've been waiting a few years.
"For the first time we succeeded in separating two vehicles flying at Mach 7."
Project boss Vincent Rausch earlier said the $230m programme "could mark the beginning of a revolution in aviation and spaceflight".
WORLD AIR SPEED RECORD
X-43A flew at 7,700 km/h (4,780 mph), Mach 7
Previous record for jet held by SR-71 'Blackbird' spy plane, flying at Mach 3.2
Experimental X-15 plane flew at Mach 6.7, with rocket engine
Scramjets burn hydrogen but take their oxygen from the air, which is forced into the engine at very high speed.
Rocket engines have to carry their own source of oxygen. The term scramjet stands for supersonic combustion ramjet.
Cheaper space travel
The technology could eventually pave the way for faster long-distance air travel and cheaper access to space. But that is many years away, says the BBC's Jon Leyne in Washington.
Experts estimate that the first manned craft powered by a scramjet would not take to the air until the year 2025.
At 12,000m the scramjet was released on its Pegasus rocket
Saturday's mission began when a B-52 bomber carrying the 3.7m-long prototype aircraft under its wing took off from Edwards Air Force Base in California.
Once the bomber reached a cruising altitude of 12,000m (40,000 ft), the wedge-shaped research vehicle was released from under the wing.
Its speed was initially boosted by a Pegasus rocket, which fell away at about 30,000m (100,000 ft) leaving the X-43A to fly under its own power for 10 seconds.
The aircraft then glided through the atmosphere, conducting a series of aerodynamic manoeuvres for about six minutes before finally splashing down into the Pacific Ocean.
The mission marked the first time a non-rocket, air-breathing scramjet engine had successfully powered a vehicle in flight at hypersonic speeds.
An attempt to fly an X-43A three years ago ended in the destruction of the vehicle when its launch system failed.