CHICAGO (AP) -- United Airlines will immediately begin installing steel bars on the cockpit doors of all its planes, and other airlines are also considering new security measures to protect pilots and calm nervous passengers.
United officials say they've obtained a waiver from the Federal Aviation Administration that allows the airline to install the bars and locking hardware without going through an approval process.
"We're going to move quite aggressively to install these," United spokesman Joe Hopkins said Tuesday. "We think it's a good move."
Hopkins said the Elk Grove Village, Ill.-based airline is already talking with vendors and the bars should be on the doors within "a matter of weeks.
Alaska Airlines has also begun installing crossbar locking devices on its cockpit doors, according to officials of the West Coast regional carrier.
The steel bars are designed to protect pilots from forced entry into a plane's control center -- which apparently happened Sept. 11 on four commercial airliners that were hijacked and then crashed. The devices, however, have raised other safety concerns.
Aircraft maker Boeing says it won't participate in any retrofitting of its planes because it worries the bars could prevent an emergency cockpit evacuation. Some flight attendants have also expressed concern about not being able to access the cockpit if pilots become incapacitated.