Around the World in 67 Hours

The GlobalFlyer looks like a trimaran, with 13 gas tanks, three fuselages and a minuscule cockpit. Its one engine sits atop the plane, which has a wingspan of 114 feet, comparable to a Boeing 737. To save weight, the plane dispenses with some equipment considered essential in most airplanes, such as radar.

A spokesman for the mission said the fuel problem surfaced when sensors in the 13 tanks indicated that the plane was burning fuel at a faster rate than anticipated. The ground control crew had to assume that 2,600 pounds of fuel from the original 18,000 were gone. It was still not clear Thursday why the fuel loss occurred. The flight was the first time that the tanks had been completely full.

"We are still puzzled," said Elbert L. "Burt" Rutan, an aircraft innovator based in Mojave, Calif., who designed and built GlobalFlyer with his chief engineer, Jon Karkow.

"The fuel consumption as measured by a flow meter showed that everything was" fine, Rutan said in a telephone interview. "But the gauges showed a loss."

The aircraft either somehow vented 2,600 pounds of fuel over the side during its climb, "or we never put the fuel on to begin with -- it's either one or the other, and we still don't have a good answer."

Even with the shortfall, though, "we managed to talk Steve into flying slower" and more efficiently. "When you're tired, you want to get home faster, but we had to slow him way down."

Rutan's prop-driven Voyager in 1986 carried his brother, Dick, and a co-pilot on the first nonstop, no-refueling flight around the world. Last year, a Rutan-designed rocket won the $10 million Ansari X Prize as the first commercially built spacecraft to fly a person into suborbital space twice within two weeks.

"Voyager was a full nine-day adventure, flown at low altitude without a pressurized cabin," Rutan said. "At that time, I didn't think it was possible with jet engines, which are much less efficient."

The secret, he said, was advances in "structure and aerodynamics" achieved much more easily and inexpensively with modern construction techniques. "We had to build a plane that was 82 percent fuel, by weight, rather than 73 percent, like Voyager."

Crouch, from the Air and Space Museum, pointed out that both the balloon gondola from Fossett's 2002 "Bud Light Spirit of Freedom" and Rutan's Voyager are already on display in the Air and Space Museum, adding, "I wouldn't be surprised" if GlobalFlyer ends up there as well.

Romano reported from Salina; Gugliotta from Washington.