MINDEN " Rescue teams on Thursday expanded the territory in which they are looking for missing aviator Steve Fossett to 10,000 square miles across California and Nevada, an area the size of Massachusetts.
They also announced they will be searching a lake in northwestern Nevada, using sonar to determine whether the multimillionaire adventurer might have crashed and submerged beneath its surface.
"As you can imagine, trying to make that needle stand out in a haystack that big is going to be a real challenge," Nevada Civil Air Patrol Maj. Cynthia Ryan told reporters during a Thursday morning news conference. "It's going to be frustrating for a lot of people who were hoping for results early on."
Ryan said the intensive aerial, ground and water search for Fossett could last two weeks or longer.
"So four days into it, we are still scratching the surface, trying to raise the cumulative probability of detection," she said.
Air crews were making multiple passes over the same areas but at different times of the day so they could see them under different conditions. The jagged peaks and steep canyons of the region cast shadows that can interfere with the views of search crews.
The search area is 200 to 300 miles wide and stretches 120 miles south from the small town of Yerington, Nev., to Bishop, Calif., on the eastern side of the Sierra Nevada.
Ryan said it now also includes the Black Rock Desert far to the north, the site of the annual counterculture Burning Man gathering. Ryan would not explain why authorities had decided to search the vast plain north of Reno, but it's where land speed records have been attempted in the past.
Fossett was on a mission to study possible dry lake beds for a planned attempt to break the world land speed record when he disappeared on Monday.
The search also for the first time will include a massive body of open water.
Nevada Highway Patrol Trooper Chuck Allen said the Washoe County Sheriff's Department will send a sonar-equipped boat to Walker Lake to search for objects under the surface. Drought and farm irrigation have shrunk the lake, which is about 85 feet deep.
"It will allow people on the boat to rule this area out as a potential place the plane could have ended up," he said Thursday.
The lake is about 15 miles northeast of the Flying M Ranch, the sprawling estate owned by hotel mogul Barron Hilton where Fossett was staying when he left on his ill-fated flight. The lake and ranch are separated by Mount Grant, an 11,239-foot peak.
Walker Lake, 18 miles long by 3 miles wide, is a remnant of the ancient Lake Lahontan that covered much of central and northern Nevada during the last Ice Age. A popular fishing spot, it is bordered on the north by the Walker River Paiute Tribe's reservation and on the south by the Hawthorne Army Depot, where some 300,000 tons of bombs and other munition are store.
The expanded search area comes on the third full day of search-and-rescue operations and four days after Fossett was reported missing.
The effort has at times frustrated rescuers, who have followed a number of false leads.
"I would ask that you give us a chance and let us show you what we can do," Ryan said Thursday. "We can't always guarantee the right result that everyone would like, but I do guarantee results."
A squadron of 10 airplanes and helicopters was continuing the search in what pilots said were optimum conditions, with clear skies and light winds.
"We're going to find this guy, but it's a big country," said Nevada Civil Air Patrol Maj. Terry Vanzant.
National Guard C-130s and helicopters with infrared and thermal imaging equipment scoured the soaring peaks and sagebrush desert of northwest Nevada overnight, but the flights failed to reveal anything new.
Fossett disappeared after taking off from the Flying M ranch's private airstrip to scout sites for an attempt at a land-speed record in a rocket-propelled car. He was scheduled to be gone only a few hours and was reported missing when he did not return.
He did not file a flight plan, which is not unusual for pilots of small airplanes but has complicated the search.
Also Thursday, crews were searching for an object that was spotted about three miles south of Yerington, near the ranch where Fossett was staying. Ryan said the search crews did not have their hopes up, however.
"It could be a wrecked car," she said.
Fossett's single-engine plane, a Bellanca Citabria Super Decathlon, carried both water and food, but there also were troubling signs.
The missing plane's locator device has not sent a signal, there has been no communication from the plane's radio, and an emergency wristwatch Fossett wore to signal his location has not been activated.
Fossett is familiar with danger and high-octane rescues, after years of breaking " or attempting to break " speed and distance records on land and by air. He has held 116 such records.
In 1996, Canadian authorities sent crews to search the Bay of Fundy off New Brunswick after Fossett sent a distress signal during an early attempt to be the first person to circumnavigate the globe in a balloon.
Fossett decided to abort the flight after his electrical system failed off the Canadian coast. He landed in a farmer's field near the Maine line.
In August 1998, he had to be rescued after his balloon crashed into the Coral Sea about 500 miles off Australia's coast during his fourth attempt to circle the globe. It plunged 29,000 feet after it was struck by hail and lightning during a fierce storm.
Fossett finally succeeded in circumnavigating the globe in a balloon in 2002, and three years later became the first solo pilot to circle the globe in an airplane without refueling.