RENO (AP) -- The weeklong search for Steve Fossett has turned up no clues about the renowned aviator's whereabouts, but it has revealed a graveyard of small airplanes that crashed -- sometimes decades ago -- in the remote landscape of western Nevada.
The sightings have given rescuers one false hope after another. The latest were Sunday, when search planes spotted two more old wrecks, one of them from a U.S. Navy plane.
"Once again, you had your hopes raised and dashed, just as we have," Nevada Civil Air Patrol Maj. Cynthia Ryan told reporters during an afternoon news conference.
Search teams have discovered about one uncharted wreck a day since the intensive search began on Tuesday. To some, that is an ominous sign for rescuers struggling to find Fossett, suggesting it may be years before his fate is known.
"That's always a possibility - that he may never be found," Lyon County Undersheriff Joe Sanford said. "But I'd like to believe that with our state-of-the-art technology, the chances of finding him are much better."
That technology has so far failed to produce. It included highly sophisticated and precise imaging equipment on a Utah Civil Air Patrol plane and infrared equipment on C-130s and helicopters.
Leaders of the search-and-rescue operation have tried to put the best face on the discoveries of previously unknown plane wrecks. At the very least, they say it has demonstrated that crews can indeed spot small planes from the air.
The search teams were trying to remain optimistic but acknowledged the futility was beginning to take its toll. Sunday's false alarms further dampened spirits in the operation headquarters at the Minden Airport.
"The mood is very somber but very focused," Sanford said.
The latest developments came the same day the search operation began concentrating on an area within a 50-mile radius of the private ranch where Fossett was staying when he disappeared. That decision was based not on a hard lead, but rather on a history of airplanes crashing near runways.
The Navy plane found Sunday was in Mineral County, 45 to 55 miles east of the Flying M Ranch, which is owned by hotel magnate Barron Hilton and is about 80 miles southeast of Reno. The location of the other old wreck was not immediately released. It also was not known whether the crash sites found Sunday had been previously charted.
The 63-year-old aviator has been missing since Labor Day, after he took off from the ranch's airstrip for what was supposed to be a three-hour flight. He was said to be looking for dry lake beds where he could make an attempt to break the land speed record.
Through a week of scanning the state's rugged terrain, crews have spotted at least six plane wrecks that had been unknown to aviation authorities. Unearthing so many in such a short time has been a stark demonstration of the odds against finding Fossett's single-engine Bellanca Citabria Super Decathlon.
He is lost in one of the most remote regions in a state that is filled with vast, empty spaces.
"There's some pretty big areas in Nevada and there's some pretty rough terrain," Gov. Jim Gibbons said. "It is a challenge. It's a big challenge."
The Florida-based Air Force Rescue Coordination Center, which is helping coordinate the search, maintains a registry of known plane wreck sites in Nevada and other states.
There are 129 on the registry for Nevada. But over the last 50 years, aviation officials estimate there have been more than 150 uncharted crashes of small planes in Nevada, a state with more than 300 mountain ranges.
The area being searched for Fossett is 17,000 square miles, about twice the size of New Jersey, and is dominated by mountain ranges with peaks rising from 10,000 to 11,000 feet. Those ranges are carved with steep ravines and their slopes covered with sagebrush and pinon pine, features that can easily hide a small airplane.
Once the search for Fossett is over, or significantly scaled back, inspectors from the Federal Aviation Administration likely will be sent to each of the newly discovered crash sites. They will try to identify the pilots and bring closure to their families, agency spokesman Ian Gregor said.
The planes' owners can be traced through tail and serial numbers, as well as any identification or personal effects found at the scene, he said.
"Our inspectors will do forensic analyses of them and try to determine how the planes crashed," Gregor said. "An experienced inspector can glean a lot of information even from badly damaged or deteriorated wrecks."
National Transportation Safety Board investigators also plan to examine each of the wrecks, agency spokesman Terry Williams said.
No human remains have been found at any of the crash sites discovered so far. But that's not a surprise, given that at least two of them are decades old. The region, a largely unpopulated wilderness, also is home to coyotes and mountain lions.
News of the old wrecks has prompted inquiries to Nevada authorities from people throughout the country who wonder if the pilots or passengers may be long-lost family members.
Earlier last week, rescuers thought they had found Fossett when a search plane spotted wreckage, and cheers erupted in the control room. A helicopter was sent to the scene, but its crew quickly determined the plane was not their target.
"We received an e-mail from (a Florida man) and he said, 'You know, that could be the wreckage of my father's airplane and it dates back to 1964.' He said if we can possibly find out any more he'd be happy to know about it," Ryan said.
Days later, crews spotted another uncharted wreck, this one from a plane last registered in Oregon in 1975.
Efforts to identify the pilots of those lost planes will take a back seat to the search for Fossett, said Mike Strickler of the Air Force Rescue Coordination Center.
"If they find what appears to be an old crash, then it's a recovery and doesn't have the same priority," Strickler said. "It may take awhile before we learn more" about them.
Although Fossett did not file a flight plan, searchers still hold out hope for a miracle, said Sanford, the Lyon County undersheriff.
The operation includes more than 40 airplanes and helicopters, some of which are based at the private ranch where Fossett was staying when he began his flight.
"With the resources and assets we have, I feel comfortable we'll find the plane in the near term," Sanford said. "Whether it'll be by us, a hunter or a skier, we'll find it. I like to believe the glass is half full."
-- Associated Press Writer Sandra Chereb in Minden, Nev., contributed to this report.