Was just reading all these replys and thought I would add a couple of points.
1. I was lucky to have a jump seat ride with a captain friend of mine in a 737-300. If the cockpit door was rammed at this point the jump seat and pax would be a very big barrier for the intruder(S) and cause a delay at least, in the mean time the Capt or the F/O could get the axe out and do the business.
2. About 8 years ago I was on a flight from London-japan. Asked if could go up to the cockpit "no problem was the reply" had a good chat with the crew, could not see much as it was night so asked if I could be there for the landing, mmm I will have to ask the skipper! I thought that was it, 10mins before landing a hostie took me to the flight deck for the landing at osaka in a 747-400 wow what a buzz. I will remember it forever.