MINDEN - Search teams dramatically expanded their hunt for wealthy adventurer Steve Fossett on Thursday as rescuers began to express frustration with the task of finding a small plane in one of the most expansive stretches of wilderness in the country.
On the third full day of the search, air crews extended their flights over an area encompassing 10,000 square miles in California and Nevada. They began using sonar on a lake near the ranch where Fossett was staying when he disappeared and even sent aerial crews far to the north to fly over the Black Rock Desert, the site of the annual Burning Man counterculture gathering.
The latest developments suggested that search teams not only lack clues about Fossett's location but also do not have a good idea of which direction he was flying when he took off Monday morning from a private airstrip owned by hotel mogul Barron Hilton.
"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."
Ten airplanes and helicopters made repeated passes over a search area the size of Massachusetts that is marked by barren 10,000-foot peaks and is known for its unrelenting harshness.
Small observer planes joined military aircraft in the search for Fossett's single-engine Bellanca Citabria Super Decathlon.
Despite a massive search this week, there have been only a few false leads and no signs of the downed plane, no radio messages and no signals from the plane's emergency locator device.
The best hope was that the world-famous adventurer used his long-proven survival skills to stay alive, rationing the food and water that was in the plane.
Pilots and other crew members who have been flying over the area in northwestern Nevada and eastern California said they are trying to avoid getting discouraged as the search moves into a potentially more difficult phase.
The terrain - a mix of bare desert playas, ravines and mountain ranges - makes the quest to find Fossett especially tough.
"It is difficult to see anything on the ground unless it's a semi-truck on the road," said Robert Todd, a Nevada Civil Air Patrol pilot involved in the search. "But an airplane that's hiding from you, if you will, is not going to be seen readily."
Todd and Randy McLain, another Civil Air Patrol officer searching for Fossett, recalled previous air searches that were unsuccessful. Wreckage was found later by hikers or hunters.
"It's really difficult. You can be right on top of the aircraft and still not see it," Todd said.
The search for the 63-year-old aviator has captivated attention worldwide because of Fossett's past exploits and his connection to British billionaire Richard Branson, who has bankrolled many of Fossett's missions.
Fossett, 63, became rich operating a series of Chicago-based investment firms before turning his attention to long-distance and high-speed pursuits.
He has set 116 land and air records, including the first person to circle the globe in a balloon and the first to do so in a plane alone without refueling.
Many of his pursuits also have ended in failure, requiring costly and daring rescues. That included a 1998 attempt to circumnavigate the globe that ended when his balloon crashed into the Coral Sea about 500 miles off Australia's coast.
"This man is such an adventurer, a man's man if you will," Todd said. "He would probably walk out 30 or 40 miles pretty easily - if he were still able to. But if he's hurt, then he may not be able to."
The search area is now 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. To the north, authorities also scanned the Black Rock Desert.
The Black Rock is a well-known testing ground for high-speed vehicles, and authorities ordered the fly-overs on the off chance Fossett went there, Nevada Highway Patrol trooper Chuck Allen said during a late afternoon news conference.
He was searching for dry lake beds to use for a planned attempt to break the land speed record when he disappeared.
Fossett didn't file a flight plan, which is not unusual for pilots of small airplanes. But that has added another complication to the search.
Pilots have said the older-model locator device on his plane easily could have been damaged. On Tuesday, the National Transportation Safety Board urged Congress to mandate use of new digital emergency locator beacons that are more reliable and emit a stronger signal.
The sense of urgency in trying to determine where Fossett went was evident Thursday when authorities began using sonar to search Walker Lake, about 15 miles northeast of the private ranch where Fossett had been staying. They hoped to rule it out as a possible crash site.
The Nevada National Guard also was using night flights that employed thermal imaging to keep the search going around the clock. It could last for weeks, said Ryan, of the Civil Air Patrol.
"We have every intention of working this search until we come to a conclusion where we know what happened, (so) we can achieve some sort of closure on behalf of the family and friends," she said.