I know that flight crew bid their schedule once a month. However, I was wondering how aircraft get their flying schedule. I know that there are so many factors involved like seat count, distance, regulations (ETOPS, overwater equipped), scheduled maintenance and I'm sure there could be more.
So, how is the flying schedule for a particular aircraft made? Who is in charge of making this schedule at the airline? Also, when an aircraft is subbed on one of its segments (let's say on YYZ-YUL, an A320 gets subbed with an E190), what happens to its remaining segments (let's say it was scheduled to fly to FLL next)?