Investigators looking into the disappearance of American adventurer Steve Fossett in the Nevada Desert have reportedly claimed the millionaire pilot may have faked his own death.

Fossett, who in 2002 became the first person to circle the world solo in a hot air balloon, sparked the biggest search in US history in September when he vanished while flying a light plane.

His wife, Peggy V. Fossett had him declared legally dead five months later after the search found no trace of him.