Washington ? Work hours would be shortened for pilots who fly at night while some pilots who fly during the day could spend more time in the cockpit under a government proposal to help prevent dangerous fatigue.

The Federal Aviation Administration plan, which the agency has spent 15 months drafting, is an attempt to overhaul pilot work rules to reflect current scientific understanding of how fatigue impacts human performance and prevent errors that cause accidents. The rules were last updated over two decades ago and most date back to the 1940s.

The proposal released Friday would bar airlines from scheduling pilots to be on duty — a combination of being at work ready to fly or in the cockpit flying — longer than 13 hours in a 24-hour period, three hours less than current regulations. At night, that limit could slide to as few as nine hours. However, airlines would be allowed to schedule pilots who start their work day between 7 a.m. and 1 p.m. for as much as 10 hours of actual flying time — two more hours than currently allowed.

Airlines would also have to allow pilots nine hours of rest between work days, an increase of an hour. Pilots have complained that the current eight-hour rest period, which begins as soon as they leave the plane, often means only a few hours sleep.

The proposed work rules would apply to all airlines, including cargo carriers and charter airlines. Cargo carriers — especially package delivery services — do much of their flying at night. Charter airlines fly 95 percent of U.S. troops and 40 percent of military cargo around the world. Charter carriers had urged FAA to maintain current exemptions to pilot work rules for their industry. But FAA Administrator Randy Babbitt said at a news conference that troops are as deserving of well-rested pilots as any other airline passenger.

Airlines — especially cargo carriers — would have to hire more pilots or revamp their flight schedules to meet the new rules. FAA estimates the proposal would cost airlines $1.3 billion over the next 10 years.

To Transportation Secretary Ray LaHood, the proposal represents “a significant improvement in air travel safety.” He acknowledged that it took FAA and his department longer to craft the proposal than he would have liked, but he said they are going further than any previous administration to address a long-recognized safety problem.

Airline industry trade groups and pilot unions said they were reviewing the proposal. The public has 60 days to respond.

The impetus for the changes was the crash of Continental Connection Flight 3407 near Buffalo, N.Y., in February 2009 that killed all 49 people aboard and a man on the ground. A National Transportation Safety Board investigation found that both pilots on the flight were probably suffering from fatigue, although that wasn’t a direct cause of the accident.