In their quest to find missing aviator Steve Fossett, searchers have come across uncharted plane crashes six times. But none of the wrecks shed light on what may have happened to the multimillionaire.

Hopes that a wrecked plane spotted on the side of a hill might be Fossett's were dashed quickly Friday when ground crews learned the plane last was registered more than three decades ago.

As the search for Fossett stretched into its fifth full day Saturday, weary rescuers were no closer to understanding where he was flying or where his small plane might have gone down.

Searchers tried to glean any positive news they could from the old crashes they discovered from an otherwise discouraging week.

"This does give us hope. We are finding a lot of stuff we didn't know was there," Civil Air Patrol Maj. Cynthia Ryan said.

Ryan said authorities had received hundreds of tips from the public since Fossett was reported missing Monday after taking off from a private airstrip owned by hotel mogul Barron Hilton 80 miles southeast of Reno.

Click here for photos of Fossett.

Authorities were concentrating on four leads they considered credible that came from people who live in, or were visiting, a large area near the Nevada-California border where Fossett was believed to be flying.

Still, it's not much to go on for rescuers trying to search an area the size of Massachusetts that is crisscrossed with jagged mountain ranges, gullies and steep canyons.

"It's like you took a 500-piece puzzle and threw four pieces randomly out on the floor and tried to make sense of them," Ryan said. "It's a little hard to do."

The lack of any solid news about the 63-year-old aviator's fate is weighing heavily on his family, said Lyon County Undersheriff Joe Sanford.

He said he spoke Friday with Fossett's wife, Marilyn, and said she and other family members remained optimistic.

"Everyone here is hopeful. But I've got to tell you that the family is subdued and they're having a tough time with this," Sanford told reporters. "We're into numerous days. No one knows what happened or where he is."

Adding to the grim prospects was the revelation Friday that Fossett most likely had only one water bottle with him when he took off for what was expected to be a short flight in a single-engine plane. Authorities initially thought he had enough water to last two weeks.

Fossett was believed to have been scouting dry lake beds as possible locations for his latest thrill ride, an upcoming attempt to break the land speed record in a rocket-propelled car. He was reported missing by someone at the ranch at 1:43 p.m. Monday after he failed to return on schedule.

He did not file a flight plan, which is common for pilots of small planes heading out for quick flights.

Fossett, a former commodities trader who was the first to circle the globe solo in a balloon, is considered an expert pilot and survivalist.

About two dozen aircraft, including airplanes, helicopters and a C-130 cargo plane, flew grid patterns over the search area on Friday. Most were scheduled to return to the air Saturday morning.

Ryan said crews have a "pretty good handle" on at least half the search area.

Despite the absence of clues, searchers remain hopeful, knowing that Fossett has a history of getting out of tough jams. He has held 116 speed or distance records on land, air and water.