ST. LOUIS (AP) _ Millionaire adventurer Steve Fossett _ who has made three attempts to scale Mount Everest, mushed a dog-sled team in the Iditarod race and swum the English Channel _ has now begun perhaps his most dangerous challenge.

Fossett, 52, lifted off from just behind second base at Busch Stadium in a cold, gentle breeze late Monday night in his quest to become the first person to travel around the world in a balloon.

More than seven hours into the flight, the word was, so far, so good. As of 6:20 a.m. CST today, Fossett was between Nashville, Tenn., and Lexington, Ky., said project manager Bo Kemper.

Two other attempts at one of the last great aviation hurdles, both by European teams, ended in failure this month.

To succeed, the Chicago securities dealer will have to spend the next 15 to 18 days in a cramped, chilly gondola just 4 feet wide and less than 6 feet high. It'll be 40 degrees inside the bright yellow gondola attached to the silvery ``Solo Spirit'' balloon, while temperatures outside will be as cold as 50 below.

``He can sit in a cold, dark box for weeks on end and be happy,'' said launch co-director Bruce Comstock. ``The food's lousy and so on, but he loves doing it.''

Monday's launch was more than two hours late because of gusting winds. Still, about 200 people watched in the snow-covered stadium as the enormous, ice-cream-cone-shaped balloon floated into the darkness.

Fossett made it from Rapid City, S.D., to New Brunswick, Canada, last January, before cold, a dead heater and problems with his autopilot ended his flight. He's also trying to break his 1995 distance record of 5,435 miles.

``This is dangerous, but we do have a number of safety precautions,'' Fossett said earlier in the day, wearing a blue St. Louis Cardinals cap. ``I'm comfortable with not only the risk but our game plan, so that this won't all go to worms.''

Two European teams cut short similar attempts in recent days.

On Jan. 8, British tycoon Richard Branson and two others narrowly averted a crash on the second day of their round-the-world attempt when their balloon lost altitude at 30,000 feet. One of the crew members slowed the balloon's fast descent by crawling outside the gondola to jettison a 1-ton fuel tank. The balloon, which took off from Marrakesh, Morocco, landed in the Sahara in Algeria.

On Sunday, the attempt of Dr. Bertrand Piccard of Switzerland and Wim Verstraeten of Belgium failed six hours after they left Chateau d'Oex in Switzerland. Kerosene fumes choked off their air supply, forcing them to ditch in the Mediterranean Sea.

Fossett's route would take him over Scandinavia, Russia, China and Japan, with a landing expected in either Illinois, Michigan or Ontario. He chose to fly from St. Louis because it's just below the jet stream with fast wind speed.

Branson, in St. Louis to watch Fossett's liftoff, said his own balloon had relied on much more intricate, high-tech equipment.

Unlike other balloonists, Fossett will fly solo in an unpressurized cabin capped by a plexiglass bubble. He said flying at 18,000 to 22,000 feet, a lower altitude than the failed groups, might be an advantage.

``We're all using experimental equipment,'' Fossett said. ``We have to, because this hasn't been done before. But their equipment had less testing than mine, so I'm hopeful I won't have the same problems they had.''