PhilRigg
The BAA equation (for the union) is how many people are needed to run the security and other services and will the hard core who voted yes be able to cause the airports to close.
25% of the whole workforce coming out might be more than enough to stop things dead (although I am speculating and may be very wrong.)
I've just booked flights avoiding a London connection on 4/9 and 11/9, just in case.
That is the trouble with IA for businessmen, the threat of disruption is as good as disruption in persuading us to take action.