I recently took a weekend trip from San Diego to Toronto for the sole purpose of taking pictures of airplanes from within the terminal at YYZ. Long story short, it didn’t quite go as well as I had planned, but I was lucky enough to have booked a room at the Sheraton Gateway hotel adjacent to Terminal 3 at YYZ. Prior to booking, I wasn’t even aware that photography would be possible from the rooms – so that was a nice surprise once I checked in.
Assuming that you are on an upper floor facing the airport, the Sheraton Gateway offers incredible up-close views of the action at Terminal 3. There is some clutter between the hotel and the terminal itself (rooftop antennas, air conditioning units, etc), so it will make photographing airplanes parked nearest to the hotel kind of difficult. But you’ll have a clear view once they pull away from the gate.
It’s important to note that you will need at least a 200mm lens to get close up shots of anything, and 400mm would be ideal. Unfortunately, I only had a point and shoot with an 85mm lens so it was nearly impossible to get tight shots of anything.
I’d definitely stay at this hotel again just because it’s so good for taking pictures of airplanes. Unfortunately, as a US citizen, I’ve had nothing but frustration trying to get into Canada over the years. I’ve never been denied, but there were a few times I thought they were going to pull on some rubber gloves and show me to a private room to continue the questioning. Not worth the hassle, IMHO.