I'm curious, does your airline specify at what point your flight is considered officially dispatched? For example, is at door closing, push back, taxi under own power, or takeoff. I seem to recall from a previous job years back that they were very specific as to when an airplane was dispatched, the reason being was that it was important to distinguish between when you were to take your guidance from the MEL vs when you take your guidance from the POH/QRH. Their philosophy was that after dispatch, for all intents and purposes the FAA does not distinguish whether you are on the ground or in the air, you do not use the MEL at this point. For example you taxi out and have a problem, at this point you do not refer to the MEL or call maintenance, you only speak with your dispatcher and use the QRH/POH. Another side question which may or may not be related to whether the airplane is "dispatched" if that is even a term any more is when does the Captain officially take charge of the airplane?