"It was a full mission success," program manager Charlie Brink of the Air Force Research Laboratory at Wright-Patterson Air Force Base said in a statement.
The sleek, missile-shaped WaveRider was released from a B-52 bomber 50,000 feet above the Pacific and was initially accelerated by a rocket before the scramjet kicked in.
It reached Mach 4.8 in less than half a minute powered by a solid rocket booster. After separating from the booster, the scramjet engine was ignited, accelerating the aircraft to Mach 5.1 at 60,000 feet.
The flight ended with a planned plunge into the ocean.
The WaveRider traveled more than 370km in six minutes, making it the longest hypersonic flight of its kind. Engineers gathered data before it splashed down.
Darryl Davis, president of Boeing Phantom Works, which built the WaveRider, called the test "a historic achievement that has been years in the making".
"This test proves the technology has matured to the point that it opens the door to practical applications," Davis said in a statement.
While the Air Force did not have immediate plans for a successor to the X-51A, it said it will continue hypersonic flight research.
- AP
