FORT WORTH, Texas (AP) _ Buckle up, and stay that way.

American Airlines is becoming the first carrier to require passengers in their seats to keep their lap belts fastened from takeoff through landing. Currently, passengers may unbuckle during the flight if the pilot turns off the seat belt light.

``People in their seats need to be belted in,'' American spokesman Tim Smith said Monday. ``We've had that as a recommendation to passengers for a long time. It is clearly the best way to deal with unexpected turbulence from a safety standpoint.''

United Airlines said late Monday it would follow American's lead. Delta, the other Top 3 airline in the nation, said it would not change its rules but would watch to see how the new policy works out at the other airlines.

The new policies on American and United will have passengers doing what is already standard practice for the captain and co-pilot.

The new policy is aimed at protecting passengers from clear-air turbulence _ areas of unstable air that can buffet a jet without warning.

``We don't think it's a burden to keep the seat belt fastened if you're seated,'' said United spokesman Joe Hopkins.

A United Airlines jet flying from Tokyo to Honolulu hit clear-air turbulence in December that killed one passenger and injured 83 others.