UA 93: How did the alleged hijackers manage to enter the cockpit?

[John Doe II]

Based on Spooked911's thead about the seven crew members vs four alleged hijackers we come to a very simple question:

How did the alleged hijackers on UA 93 manage to enter the cockpit?
The same question goes for all four planes.

It is normally described that they opened the door and killed the pilot before he even had the time to turn around. The alleged hijacker simply used the advantage of the surprise attack.


But the problem is that it simply can't have been that easy!
The cockpit door was locked.
Let's listen to Jere Longman who wrote "Among the Heroes":
"Dahl and Welsh had established the secret-knock sequence that she would use to enter the cockpit. The code was changed on every flight. United flight attendants did not carry cockpit keys, which were to be used for emergencies. One key was always located in the forward part of each aircraft, sometimes in the galley, but nota lways in the same place"
(p. 8)

"In the event of a hijacking, flight attendants were to phone the cockpit and mention the word "trip".
(p.9)

Spooked911 comments:
"This tells us:
1) that the crew locked the cockpit doors, so the hijackers could not have just walked in, they would have to smash the door open.
2) the pilots can hear knocks on the cokpit door. If they can hear knocks, they can hear someone trying to ram open the cockpit door.
3) the crew members were prepared for a hijacking!

There is simply no way the UA93 pilots could have been taken by surprise."

Jere Longman precised:
"Although (b] the cockpit door remained locked during flight, it provided only flimsy protection on September 11. The door was designed to withstand no more than one hundred and fifty pounds of pressure , so that it could be forced open in emergencies, allowing the pilots to escape outward or passengers to escape inward to climb out of a cockpit window. A heavy shoulder would dislodge the door."
(p. 8)

Problem would be if you push this door very hard and it opens you are in no good attacking position as you will fall down on the floor or have to regain your balance at least. No chance that you can kill the pilot before he even had the chance to turn around.

And as far as I can recall no phone call of the passengers speak of hijackers pushing violently the door open. But I'll have to countercheck this.

Even stranger:
Why didn't the at least six passengers being much more athletic than the hijackers not manage to open the very same cockpit door although they had even the help of a foot car and the fight lasted six minutes?