US National Guard C-130s and helicopters with infrared and thermal imaging equipment scoured the soaring peaks and sagebrush desert of northwest Nevada early on Thursday for any sign of missing adventurist Steve Fossett.

Fossett disappeared Monday after taking off from a private airstrip in a single-engine plane to scout sites for an attempt at a land-speed record in a rocket-propelled car.

The painstaking search across more than 1,555 square km has covered only a fraction of the territory that could be hiding the airplane. Finishing the fly-overs of the most likely landing spots could take another week. The Civil Air Patrol and additional flight crews were scheduled to resume a full search after daybreak.