Steve Fossett's attempt to circle the globe in a balloon has entered a critical period as weather and fatigue prove to be tough adversaries.

"We really don't know at this point where the balloon wants to go," said Bob Rice, meteorologist for Fossett's mission control at Washington University in St. Louis.

The Chicago millionaire, making his fourth attempt to fly around the globe, was approaching the halfway point of his journey. But he was in danger of being drawn into a high-pressure system over the Indian Ocean that "would make him loop and go nowhere," said Alan Blount, control center director.

Thursday afternoon, however, trackers saw a tendency for the balloon to turn right, which would indicate Fossett had found a layer of winds that would get him out of danger and put him on a path toward Australia.