But it does depend on your commute and if the elements conspire against you!
Exactly. I do a lot of flying and it depends on where I am and the way I am travelling to the airport. Here at home with a 15-20 minute drive along quiet country roads I will leave an hour and a half before my flight takes off. 20 minutes to the airport, straight through fast track security and time for a quick drink in the lounge before I go to the gate. If I'm in a busy city and travelling to the airport by road I will aim to get to the airport at least two hours before the flight to allow for traffic or, if it is a city I know well, I will travel by metro to avoid any delays on the way to the airport.