These days the winter period is not the quiet winter period it used to be. Airlines need to use the aircraft as much as they can all year. It is a bit quieter, but then there are ski flights, Santa Claus flights, ad hoc charters, etc. and many airlines have agreements with other airlines for swapping pilots. First Choice have an agreement with a Canadian airline, which sends its pilots to the UK for the summer and then we send some pilots to Canada for the winter. This means the airline can employ less pilots and still be fully crewed for the busier summer period.