American adventurer Steve Fossett has passed the halfway point of his attempt to fly a balloon solo around the world. Mr. Fossett has crossed South America's Andes Mountains and is now drifting toward the Atlantic Ocean.

After drifting slowly and quietly over the Pacific Ocean for the last several days, Steve Fossett hit some rough air Thursday, about an hour after he crossed a 6,700 meter-high mountain peak in South America. Jim Mitchell is a spokesman at Mr. Fossett's flight control center in the U.S. city of St. Louis. "He got shaken up this morning coming across the Andes," he said. "As you know, when you fly over a mountain area, the terrain interrupts the even flow of the wind and you get a certain amount of turbulence. He struck that this morning and was thrown around a little bit and thought there was some danger of rupturing the balloon."

Mr. Fossett strapped on his parachute just in case, but told his flight controllers the winds had calmed after about 30 minutes. Three years ago, Mr. Fossett was nearly killed when a thunderstorm off the coast of Australia shredded his balloon, sending his capsule plunging 9,000 meters into the Coral Sea.

Mr. Fossett lifted off from Western Australia August 4 on his fifth try at becoming the first solo balloonist to circle the Earth. Now that he has crossed the Andes, he will fly the balloon at lower altitudes. Flight controllers say that will help him avoid thunderstorms over Uruguay, catch favorable winds that will push him over the Atlantic toward the southern tip of Africa, and allow him to fly without having to breathe from his oxygen tanks. Mr. Fossett only has about five days worth of oxygen left, though his flight team says he should be able to cross the Atlantic without using his oxygen mask very often.

Mr. Fossett has flown for just about 12 days, making this the longest solo flight and the second-longest balloon flight on record. In 1999, a two-man crew completed a round-the-world balloon flight.