A Ukrainian-Russian rocket carrying a telecommunications satellite plunged into the Pacific Ocean shortly after launch on Friday.
The Zenit-3SL rocket, which was being operated from a floating pad south of the Hawaiian islands, failed 40 seconds after the lift-off at 6:56 GMT.
The Intelsat-27 satellite was due to be positioned over the Atlantic to provide services to America and Europe.
The international Sea Launch consortium has used the former Pacific Ocean oil platform to perform commercial launches since 1999. Prior to Friday's launch there had been only two complete failures in 34 missions.
The Ukrainian-Russian Zenit-3SL vehicle has a generally good reliability record.
A modified version, the Zenit-3SLB, is operated from land, flying out of the Baikonur Cosmodrome in Kazakhstan. The most recent of these launches was at the end of 2011.
Intelsat-27, which weighed 6.2 tonnes, was to have provided direct-to-home TV services and mobile broadband connections.