I am a Prestige member flying YYZ-LHR on the 11:55pm flight on Sunday (AC858) in Y. I am on a B fare so do not expect to be able to use an upgrade . However, my TA is insisting that I must be at the airport 3 hours in advance for an international flight. Given the time of day, and that T1 airport must be close to deserted by then, is this really true? If I do not get there until 10:30pm, would I have a problem?

Thanks for your input. I appreciate it.