Absolutely. Remember this is a group (AQ) with demonstrated expertise in learning from experience and who track our doctrine and cultural philosophy. The moment the state militia aboard flight 93 reported for duty and subsequently accomplished their mission (God Bless them) the AQ was preparing a counter. They now know after watching the ugly scene of the shoe bomber Richard Reid that the passengers will no longer act like sheep in the face of a hijacking. The entire aircraft will fight like animals to the end. Also they know that we are arming both our flight crew in the cabin, teaching unarmed combat to flight attendants and sticking highly trained (??) and loaded fer bear sky-marshals on board target aircraft. IF they think they can get a big bang for the buck out of another hijack, they will train for all of these contingencies. That means that despite all of the foregoing, they still think they can pull it off.
So the bathroom thing may actually be for combining otherwise innocuous chemicals to temporarily disable personnel?
They need to control the aircraft in order to hit our most "sensitive" targets, right? Flight 93 was headed somewhere in DC.
So logical reasoning would lead one to surmise that an airline takeover would necessitate the incapacitation of all passengers and/or crew.
This puts the rash of emergency/diverted landings in the last few weeks due to smoke or fumes on board in a glaring light.