The Defense Advanced Research Projects Agency (DARPA) said it had recently completed a free flight test of an aircraft-launched hypersonic missile that maintained a speed of more than Mach 5, or five times the speed of sound (at least 3,800 miles per hour, or 6,100 kilometers per hour).

The missile flew to an altitude greater than 65,000 feet (19,800 meters) and soared over 300 nautical miles, said DARPA, the Pentagon's high-tech research body.

It was the second test under the agency's HAWC Program -- named for hypersonic air-breathing weapon concept -- and the missile had a different configuration from the first, which was tested last September.

According to CNN, the newest test took place in mid-March but was kept quiet to avoid appearing to escalate the geopolitical tensions surrounding the Russian invasion of Ukraine.

In March 2020, the US army and navy undertook a joint test of a different hypersonic prototype.

DARPA said air-breathing hypersonic missiles use air captured from the atmosphere to help sustain propulsion.

"This Lockheed Martin HAWC flight test successfully demonstrated a second design that will allow our warfighters to competitively select the right capabilities to dominate the battlefield," said Andrew Knoedler, HAWC program manager, in a statement.

Hypersonic missiles pose a potential threat to the global military balance, capable of being steered to deliver nuclear weapons precisely on target, at speeds too fast to intercept.

The Pentagon is under pressure to match China's apparent successful test of a hypersonic missile last year that flew around the globe and hit a target in China.

Russia also claimed two weeks ago to have fired two hypersonic missiles in strikes on Ukraine.