WASHINGTON (AP) — Nearly three years after the deadly crash of a regional airliner flown by two exhausted pilots, the Federal Aviation Administration is releasing rules aimed at preventing airline pilots from flying while dangerously fatigued.

The pilot work schedule rules, which were expected to be made public Wednesday, have been the focus of rival lobbying campaigns by pilot unions and airlines since the FAA released a draft proposal more than a year ago.

That proposal was a mixed bag: Work hours would be shortened for pilots who fly at night, while some pilots who fly during the day could wind up spending more time in the cockpit. Pilots would be required to have a minimum of nine hours off to rest between work shifts, one hour more than under present rules.

Researchers say fatigue can impair a pilot's performance by slowing reflexes and eroding judgment, much like alcohol. The National Transportation Safety Board has been campaigning for two decades for an overhaul of pilot work schedule rules. An effort by the FAA in the late 1990s to develop new rules stalled when pilot unions and airlines were unable to find common ground.

The effort was revived after the February 2009 crash of a regional airliner near Buffalo, N.Y., killing all 49 people aboard and a man on the ground. An NTSB investigation found that both pilots were probably suffering from fatigue.

Neither pilot appeared to have slept in a bed the previous night. The flight's captain had logged onto a computer in the middle of the night from an airport crew lounge where sleeping was discouraged. The first officer had commuted overnight from Seattle to Newark, N.J., much of the time sitting in a cockpit jumpseat. They could be heard yawning on the ill-fated flight's cockpit voice recorder.

However, by a 2-1 vote the board decided not to cite fatigue as a contributing factor to the crash. The board agreed that the captain's incorrect responses to a stall warning caused the accident, and that other pilot errors contributed to the crash. But investigators said it wasn't possible to determine whether those errors were the result of fatigue.

The families of victims killed in the crash, however, have relentlessly lobbied Congress and the Obama administration for new regulations to ensure that airlines use schedules that give pilots enough time for rest and reflect an understanding of how travel through time zones and the human body clock's response to light and darkness can affect performance. They won congressional passage of a law requiring the FAA to issue new rules by Aug. 1 of this year, but the White House Office of Management and Budget delayed release of the rules.

Airlines for America, an industry trade association, has estimated that the draft rules would cost airlines as much as $2 billion a year and, over time, cut as many as 27,000 jobs directly tied to the industry. Much of the cost would be to hire relief pilots for longer flights and to adjust schedules, including cutting back flights to some smaller cities.

The companies argue that the cost isn't justified by the risk. U.S. airlines are in the midst of a period of exceptional safety. There have been no fatal airline crashes in the U.S. in the nearly three years since Continental Connection Flight 3407 near Buffalo. That flight was operated for Continental Airlines by regional carrier Colgan Air Inc.

Pilot unions say airlines have significantly inflated their cost estimates.

Cargo carriers like Federal Express and United Parcel Service, which do much of their flying at night, would be especially affected by the new rules. The same holds true for charter airlines that transport nearly 90 percent of U.S. troops and about half of the military cargo around world. They've urged the administration to allow them to operate under different rules than scheduled airlines, warning that some military missions could be jeopardized.

NTSB Chairman Deborah Hersman has said the industry's argument isn't credible. They can still fly the same missions, Hersman told The Associated Press earlier this year, but they may have to add extra pilots to their crews and make sure pilots have places onboard or on the ground where they can get sufficient rest before flying again.