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The Falcon hypersonic HTV-2 aircraft emerges from its payload fairing before gliding back to Earth. CREDIT: DARPA View full size image

This story was updated at 5:42 p.m. ET.

An unmanned military plane billed as the “fastest aircraft ever built” crashed into the Pacific Ocean today (Aug. 11) after a malfunction caused it to stop sending signals while flying at more than 20 times the speed of sound, military officials said.

The flying prototype, called the Falcon Hypersonic Technology Vehicle 2 (HTV-2), plunged into the ocean after shifting into a mode that allows it to fly Mach 20, or about 13,000 mph, according to the Defense Advanced Research Projects Agency (DARPA), which oversaw the Read more…