(recasts with search area expanded, night searches stopped)

By William Albright

RENO, Nevada, Sept 7 (Reuters) - The search for U.S. adventurer Steve Fossett, missing in the rugged Nevada desert for five days, was expanded again on Friday, but authorities said they were suspending night flights.

Capt. April Conway, spokeswoman for the Nevada Air National Guard, told reporters the air search had been extended to 17,000 sq miles (44,000 sq km) from 10,000 sq miles (26,000 sq km).

Conway said authorities had recalculated the fuel consumption in Fossett's small, single engine plane and thought he might have flown farther than previously envisaged.

The night flights by two planes carrying infrared technology will be discontinued from Friday because they were not yielding productive results, she said. The daytime air searches will continue throughout the weekend.

About 25 planes are flying over the mountainous terrain where the 63-year-old millionaire and aviation record-setter's plane disappeared on Monday. He was scouting locations for a planned attempt to set a land speed record.

Authorities told reporters they had followed several leads and apparent sightings over the past few days but had turned up nothing promising.

Wreckage was spotted in the Black Rock Desert, north of Reno, on Thursday, but it turned out to be a 43-year-old crash site.

Maj. Cynthia Ryan of the Nevada Civil Air Patrol said 90 percent of Nevada is restricted military airspace and that radar would detect the slightest incursion into that area.

Authorities are focusing their search on an area outside the military airspace.

Ryan said the suspected crash could remain undetected for months, noting that many previous wrecks have been discovered by hikers in the barren and mountainous terrain.

"In the spring, when the snow has melted, sometimes they find them then. But we have every intention of working this search until we come to a conclusion where we know what happened and we can come to some sort of closure for family and friends," Ryan told reporters.

Some of the aircraft are equipped with imaging technology that quickly distinguishes man-made objects, including aircraft wreckage, from natural objects.

But there has been no sign of Fossett or his plane, or any indication of what might have happened.

Searchers said they had been unable to confirm with Fossett's family that the adventurer was wearing a sophisticated watch that is designed to let pilots signal their location in an emergency.

Fossett, who has a knack for getting out of tough situations, became the first person to fly a balloon solo around the world in 2002 and made a record-setting solo nonstop airplane flight around the world in 2005.

He also climbed more than 400 mountain peaks, swam the English Channel, raced in the Le Mans auto race and competed in Alaska's Iditarod Trail Sled Dog Race.

AlertNet news is provided by