Rules aimed at preventing airline pilots from flying while dangerously fatigued were issued Wednesday by the Federal Aviation Administration, a move safety advocates have been urging for more than two decades.

The rules update current pilot work schedule regulations, which largely date back to the 1960s, to reflect studies on how much time pilots need for rest and an understanding of how travel through time zones and the human body clock's response to light and darkness can affect performance.

Carriers have two years to adapt to the new rules. The FAA estimated the cost to industry at $297 million over 10 years, a fraction of the $2 billion a year that an airline trade association had estimated a draft proposal released by FAA over a year ago would cost.

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In this Feb. 12, 2009, file photo, Continental Airlines Flight 3407 burns after it crashed into a house in Clarence Center, N.Y. (David Duprey, File/Associated Press)

The new rules come nearly three years after the deadly crash of a regional airliner flown by two exhausted pilots. Family members of the 50 people killed in the accident near Buffalo, N.Y., have lobbied relentlessly for more stringent regulations.

The rules would limit the maximum number of hours a pilot can be scheduled to be on duty — including wait time before flights and administrative duties — to between nine and 14 hours. The total depends upon the time of day pilots begin their first flight and the number of time zones crossed.

New restrictions

The maximum amount of time pilots can be scheduled to fly is limited to eight or nine hours, and pilots would get a minimum of 10 hours to rest between duty periods, a two-hour increase over the old rules. Pilots flying overnight would be allowed fewer hours than pilots flying during the day.

But cargo carriers — who do much of their flying overnight when people naturally crave sleep — are exempted from the new rules. The FAA said forcing cargo carriers to reduce the number of hours their pilots can fly would be too costly compared to the safety benefits.

Imposing the rules on cargo airlines like Federal Express or United Parcel Service would have added another $214 million to the cost, FAA officials said.

The exemption for cargo carriers runs counter to the FAA's goal of "one level of safety" across the aviation industry. It's also certain to provoke complaints from pilot unions, who point out that cargo pilots suffer from fatigue the same as pilots for passenger-carrying airlines. And, while cargo planes aren't carrying passengers, the risk to the public on the ground from an air crash is just as great.

The charter airlines that transport nearly 90 percent of U.S. troops around the world had also lobbied heavily for an exemption to the new rules, saying military missions could be jeopardized. But FAA officials rejected those pleas.

Accident prevention

The new rules give "pilots enough time to get the rest they really need to safely get passengers to their destinations," FAA Acting Administrator Michael Huerta said.

The rules will prevent about one and a half accidents a year and an average of six deaths a year, FAA officials said. They will also improve pilots' health, officials said.

Researchers say fatigue, much like alcohol, can impair a pilot's performance by slowing reflexes and eroding judgment. 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.

That effort was revived after the February 2009 crash of Continental Connection Flight 3407 near Buffalo. 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.