Millionaire adventurer Steve Fossett (search) decided Wednesday to press ahead with his attempt to fly around the world solo without refueling, despite a serious problem with the plane's fuel system.

Fossett and his flight crew agreed Wednesday afternoon to keep the GlobalFlyer (search) in the air rather than abandoning the record-setting attempt and turning back for a landing in Japan.

He was heading east over the Pacific Ocean, and the team expects to decide Wednesday night after reaching Hawaii whether to continue on to the U.S. mainland, some seven hours away.

"I'm better than I was yesterday," Fossett told reporters as he headed into daylight east of Japan. "It improves the mood, also. I'm hopeful this is all going to work out."

Fossett discovered the problem with the fuel system of the custom-built plane early Wednesday. Once the GlobalFlyer reaches Hawaii, a critical transfer of fuel from outer tanks to the plane's center booms will be complete and the team will know more precisely how much fuel is left.

Project manager Paul Moore said fuel sensors in the 13 tanks differ from readings of how quickly the plane's single jet engine was burning fuel. Moore said the crew had been forced to assume that 2,600 pounds of the original 18,100 pounds of fuel "disappeared" early in the flight.

It was not clear whether the problem was with the instruments that track how much fuel remains or if some fuel had been lost because of a leak, Fossett's team said.

"This is a huge setback," Fossett said from the plane, according to a statement issued by his staff. "I have not that high a level of confidence at this point."

Fossett, 60, still might be able to finish the flight on his original path, if a tail wind in the jet stream remains strong enough to push him across the Pacific.

Before the fuel problem was discovered, Fossett had estimated he would complete the 23,000-mile journey at midday Thursday. He took off Monday from Salina.

Fossett already holds the record for flying solo around the globe in a balloon, as well as dozens of other aviation and sailing records.

The project is being financed by Virgin Atlantic founder Sir Richard Branson (search), a longtime friend and fellow adventurer.

The first nonstop global flight without refueling was made in 1986 by Jeana Yeager and Dick Rutan (search), brother of GlobalFlyer designer Burt Rutan.