the biggest issue with AC is if you have to fly into Toronto, clear customs and change terminals there - it's a zoo. I try to go thru US, now, so I clear customs in Ottawa rather than deal with the headache. And one nightmare incident with AC is all it took (we cleared customs, made it to stand first in line at the gate, and found they had "busted" us - gave our seats away to a standby passenger because they'd made the decision we couldn't make the connection - months arguing with the Ombudsman, etc., until we finally got our out-of-pocket expenses only reimbursed - can't really pay for a 3-year old's disappointment about missing breakfast with Cindy next morning!)