1.   American had recently reinforced cockpit doors on all its planes to prevent forced entries.

2.   As has long been standard in Volvo, doors are heavily reinforced with hi-tech steel.

3.   Both bills provide for sky marshals on flights and reinforced cockpit doors, among other things.

4.   But reinforcing those doors raises complicated issues.

5.   Delta and other carriers already have reinforced cockpit doors to prevent forced entry, as required by the Federal Aviation Administration.

6.   Its cockpit door had been reinforced.

7.   Most airlines are also installing stronger locks on cockpit doors and reinforcing the doors with metal bands.

8.   Passengers have come to expect careful inspections at security checkpoints, armed soldiers in terminals and reinforced cockpit doors in airplanes.

9.   Passengers have come to expect careful, tedious inspections at security checkpoints, armed soldiers in terminals and reinforced cockpit doors in airplanes.

10.   People tended to move out of the way as soon as they spotted the four bulky army vehicles with their bulletproof windows and reinforced steel doors.