Airlines to Keep Passengers Buckled Up

American Airlines and United Airlines said they will begin requiring passengers to wear seat belts throughout their flights, from takeoff until landing, in an effort to avoid injuries from unexpected turbulence. AMR Corp. and UAL Corp., the respective parents of the carriers, both said they would probably begin enforcing the policy in the summer. Passengers would still be allowed to leave their seats after a plane has reached cruising altitude. Delta Air Lines Inc., Southwest Airlines Co. and other carriers said they have no immediate plans to adopt such a policy, adding that they encourage passengers to buckle up.