How did they do the hijacking?
Facts/Rumours so far:
- Box cutters or other small knives used (either they found something that would get past security or they would have to subvert security on a precise schedule in several locations)
- Low passenger loads (enabling small number of hijackers to overpower/hold off pax; I suspect several hijackers/plane as a half-dozen guys with knives would likely succumb to a couple hundred seriously agitated pax)
- Enough training to fly 767 (the training may not have been in a box; there are some good quality PC sim programs out there that might have been enough on top of basic pilot lessons - and I recall an instructor telling me of a 747 box where you could fly through tall buildings; so maybe they did train in a box)
- Very high degree of organisation
- CVRs will be valuable unless hijackers knew how to pull CB (digging usable CVRs out of WTC rubble may be problematic, but Pentagon and Pittsburgh CVR likely retrievable)
For what it's worth, rapid (if possible) decompression might be worth consideration as an ultimate desperation hijacker countermeasure; at least it would be hard for the hijackers to move around while remaining on O2.