WASHINGTON — One in five airline pilots lives at least 750 miles from work, according to a study by scientific advisers to the government, raising concerns that long commutes to airports could lead to fatigue in the cockpit.

The calculations were based on home addresses of more than 25,000 pilots. Six percent of pilots listed a primary residence at least 1,500 miles from the airline base where they begin flights, according to a National Research Council report released Wednesday.

Although a significant share of pilots list addresses hundreds of miles from their base, it’s not clear that they routinely begin their commutes to work from those addresses, the report said.

The council acknowledged it is difficult to determine the safety risk associated with long commutes without more information about the practices of individual pilots.

Pilot unions and airlines have long maintained that pilots can safely commute long distances to work if they act responsibly. For example, a pilot might fly across the country to reach his airline’s base but then sleep overnight in a hotel before showing up for work the next day well-rested.

“There are lots of stories and anecdotes but no systematic information,” said Indiana University professor Clinton Oster Jr., chairman of the panel.

Every pilot’s commute is unique, said Jeff Skiles, the first officer of US Airways Flight 1549, which ditched into New York’s Hudson River two years ago after striking geese.

“To have a hard and fast rule that covers everybody is almost impossible. In some cases it might help, and in some case it might hurt,” Skiles, who testified before the research panel about pilot commuting last fall, said.

Also, some pilots may list a residence in a state with a low tax rate as their primary residence, but they commute from a residence closer to their airline base, he said.

Congress directed the council to study the issue in response to a regional airline crash that killed 50 people in February 2009 near Buffalo, N.Y. The flight’s co-pilot had commuted overnight from her home near Seattle to her airline’s base in Newark, N.J., in order to make the flight. The flight’s captain, who regularly commuted from Florida to Newark, had spent the night before the flight in an airport crew lounge where sleeping was discouraged.

The National Transportation Safety Board concluded the accident was caused by pilot errors. The NTSB said it was also likely both pilots were suffering from fatigue, but the board wasn’t able to determine if fatigue contributed to crash without more information. The decision was a controversial one, with board chairman Deborah Hersman arguing in favor of finding that fatigue was a contributing factor. The vote was 2-1.

The accident drew attention to the salaries of regional airline pilots, who say they sometimes need to commute long distances because they can’t afford to live in more expensive communities where they are based. The salary of Rebecca Shaw, the co-pilot in the Buffalo crash, was less than $16,000 in the year before the accident.