Let me give you an example. Last Sat, we came from FLL to YOW. The flight was delayed by 5 hours (due to freezing rain in Ottawa). We checked in 1.5 hrs prior to the originally scheduled flight departure time.

The question is if we had checked in (lets say) 3 hours after the originally scheduled flight departure time, which would mean that it would have been 2 hours before the actual departure time, would our tickets have been in jeapardy of being cancelled?

What I am trying to ask is that if one wants to ensure that AC keeps your reservation and booking for a given flight, does one need to arrive at the airport, and check-in, at the designated time before the originally scheduled flight time, or at the designated time before the actual time of the flight departure?