United States Department of Defence’s research agency, DARPA, built the Falcon HTV-2, a hypersonic unmanned aircraft in an attempt to make long-duration hypersonic flights a reality and to give military commanders the ability to strike targets anywhere in the world within an hour. Unfortunately, the rocket-launched aircraft was lost during a test flight over the Pacific in 2011. It should be noted that DARPA built only two falcon prototypes. The first Falcon Test flight HTV 1 had to be steered into the sea after a glitch was detected. After their second loss, there are no reports of a third mission.
- Hypersonic Technology Vehicle 2 – Wikipedia