GENEVA (AP) _ A Swiss-English team hoping to be the first balloonists to circle the world nonstop opened their hatch today over the Pacific for a bit of fresh air, with nearly one-half the distance behind them, their control center said.

The two balloonists passed the 12,500-mile mark today, said project manager Stefano Albinati, almost half of the total 26,000 miles they will log if they reach North African again.

Bertrand Piccard of Switzerland and Brian Jones of England, who set out from the Swiss Alps March 1, brought their balloon down to 6,000 feet over the Pacific just before dawn today, the control center said.

``The two pilots said they are very impressed by the immense expanse of water, which is their only scenery,'' the center said in a statement.

Albinati told The Associated Press he was concerned about the Breitling Orbiter 3's speed. At just 48 miles an hour, they will be over the Pacific for another five days. ``But what can you do,'' he said.

Much depends on the weather. Storms have forced rivals in the round-the-world bid to give up, and the Breitling Orbiter's meteorologists have to try to avoid bad weather as well as try to keep the team in good winds.

The size of the Pacific also is a concern because it would complicate rescue operations if they were to go down in a remote location.

After leaving China the team had to maneuver to get winds heading in a favorable easterly course rather than move to a different altitude that would put them in faster winds heading in a different direction.

Piccard and Jones opened the hatch on top of their high-tech gondola today for the first time since they were over North Africa a week ago, the center said. They aired out the cabin and did some housekeeping.

The balloonists' weather experts have been studying which jet stream to maneuver them toward _ the Polar, which would send them over California, or the Subtropical aiming for Mexico.

``It looks now like it will be Mexico,'' Albinati said, but added that plans could change depending on winds and weather.