Hypersonic jet fails speed testThe US Air Force says its attempt to fly a hypersonic jet at Mach 6 (3,600mph; 5,795 km/h) over the Pacific failed and the aircraft was lost.
Source: Hypersonic jet fails speed test (http://www.bbc.co.uk/news/technology-19277620#sa-ns_mchannel=rss&ns_source=PublicRSS20-sa)