. If you really needed to strike, why on earth do it over Christmas
Because Christmas, and Easter, are the busiest times for the airline.
A strike during this period will cause the most disruption and give the best chance of the airline management caving-in to the demands of the CC.
. If you really needed to strike, why on earth do it over Christmas and risk losing the goodwill of the public?
I imagine the union bosses believe the public will "get over it" soon enough when it's all over, as the public are usually wont to do. People will move on and find something else to moan about when Christmas (and the strike) are over. They're probably right.
Affordable inconvenience.