There's a reason why you have schedules. On AC, the flight will NOT depart early if people have checked in and have not boarded at the gate.

This get-there-itis is highly counter-productive. If you depart early you are most likely going to be in the penalty box on arrival (or on departure if your takeoff slot is not ready) so the question is where to wait? Most pax would rather wait in the airport or at the lounge. Not in a metal tube.