Two pilots soaring over the Pacific Ocean have made history by first matching, then surpassing the 5,209-mile official world distance record for human flight in a gas balloon.

"There it is! There it is!" shouted team members at the flight's mission control in Albuquerque as a giant screen showed the helium-filled Two Eagles balloon passing the record set by the Double Eagle V in 1981.

The balloon was about 400 miles north west of San Francisco when it hit the mark and everyone inside the control room had their smartphones pointed at the screen to document the moment.

In a matter of hours, they hit another milestone in similar fashion when they reached the 5,260-mile mark, the distance - 1 per cent more than the current record - they needed to meet in their quest to establish a record under international aviation rules.

The distance still has to be confirmed by the Federation Aeronautique Internationale, a process that can take weeks.

"We're not taking any time to celebrate," said Steve Shope, head of mission control. "We have a lot of work we have to do, and we're just taking this flight one hour at a time."

The Two Eagles pilots, Troy Bradley of Albuquerque and Russian Leonid Tiukhtyaev, are aiming to set both distance and duration records with their flight from Saga, Japan, which began shortly before 6.30am Japan time on Sunday.

The duration record was set in 1978 when Ben Abruzzo, Maxie Anderson and Larry Newman made the first transatlantic balloon flight.

The pilots had been aiming for Canada until a high-pressure ridge formed off the US west coast, forcing a sweeping right turn toward Mexico, where they now plan to land tomorrow.