The Civil Air Patrol is scouring the desert for Steve Fossett's plane

Forty-five aircraft are involved in the search for the missing millionaire, who disappeared on Monday while flying alone in his small plane.

Teams have scoured an area of 10,000 sq miles (25,900 sq km) of remote terrain, as yet unsuccessfully.

One object had given rescuers hope, but it was found not to be Fossett's plane.

It was spotted south-east of the ranch from which Mr Fossett took off, but closer inspection revealed that it was not connected to him.

"Once again, you had your hopes raised and dashed, " said Nevada Civil Air Patrol Major Cynthia Ryan.

After six days of intensive searches, rescuers have not found any sign of Mr Fossett's plane, but they have spotted six planes which crashed in the desert in earlier years.

Still hopeful

The discovery of the six previously unknown wrecks underscores the difficulties of finding the single-engine plane in which Mr Fossett was flying.

I feel comfortable we'll find the plane in the near-term Lyon County Undersheriff Joe Sanford

"That's always a possibility - that he may never be found," Lyon County Undersheriff Joe Sanford told Associated Press.

"But I'd like to believe that with our state-of-the-art technology, the chances of finding him are much better."

News of the old wrecks has prompted inquiries from people wondering if the pilots or passengers may be long-lost family members.

Searchers are holding out hope of finding Mr Fossett, Mr Sanford said.

"With the resources and assets we have, I feel comfortable we'll find the plane in the near-term,", he 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."