No confirmation yet, but sources are telling Aviation Week that yesterday's attempted Mach 6 flight of the US Air Force Research Laboratory's Boeing X-51A Waverider hypersonic demonstrator was not a success - but that the vehicle's Pratt & Whitney Rocketdyne SJX61 dual-mode ramjet/scramjet engine was not to blame.

UPDATE - Wired's Danger Room tweeted earlier that a fin problem resulted in loss of control before the engine could start.

The Air Force Flight Test Center at Edwards AFB confirmed to Reuters earlier today that the X-51A and its booster were launched successfully from the B-52 mothership over the Pacific between 10.00 and 11.00am local time on Aug. 17, But there has been no news since. Details of the flight are expected to be announced today.

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