The pilots' decision to land in a severe thunderstorm and their failure to set wing panels that would have helped slow the plane on the slick runway caused the fatal 1999 airplane crash in Little Rock, a federal safety agency said yesterday.

The National Transportation Safety Board said the pilots' actions aboard American Airlines Flight 1420 were not up to their usual standards, blaming the accident on their 14-hour workday and the stress they faced while trying to land the plane in bad weather.

The plane, heading from Dallas to Little Rock, crashed after overrunning the runway, killing 11 people, including one of the pilots. Another 105 people were hurt.

The pilots decided to try landing in the thunderstorm, though they could have either waited out the severe weather because they had enough fuel or flown to another airport. They thought they had enough time to beat the thunderstorm to the runway, said David Tew, chairman of the group that looked into the flight operations.

"A pilot makes a decision based on what he sees on his radar and what he sees outside the cockpit," Tew said. "They felt like they had time."

Still, board member John Hammerschmidt observed: "Get-home-itis has contributed to many poor pilot decisions."

The NTSB called for a joint industry-government task force to reduce the incidence of pilots trying to land in thunderstorms rather than going around them or diverting to another airport.

While preparing to land, neither the pilot nor the copilot set the switch for the wing panels, known as spoilers, and neither checked with the other to make sure that the switch had been set or that the spoilers had deployed, NTSB investigators said.

The spoilers help keep the plane close to the ground, reducing its lift and putting more weight on the tires, making it easier to brake and slow the aircraft. NTSB investigators suggested that the plane would have been able to stop before the end of the runway had the spoilers been deployed.

The NTSB recommended that the Federal Aviation Administration should require both the pilot and copilot to confirm that the spoilers have been set, and that a member of the crew should make sure that they have deployed when the plane lands.

After the accident, American Airlines changed its procedures to require that the pilot and copilot acknowledge that the spoiler switch has been turned on, investigators said. The airline did not immediately respond to a request for comment.

NTSB investigators said the pilots may have made the mistake because they were tired and under additional stress while trying to land the plane during the thunderstorm. "On the basis of the evidence, staff believes fatigue was a factor in this accident," said Evan Byrne, chairman of the group that investigated the pilots' actions.

The board reiterated an earlier call for the FAA to develop new work rules for pilots. Current rules allow pilots to work 16 hours a day, eight of them flying a plane, but delays can extend pilots' workdays beyond the maximum.

The wreckage of American Airlines Flight 1420 rests at the end of a runway in Little Rock. Eleven people died in the 1999 crash, including the pilot.