Originally Posted by LightingGuy
3) If he has a US passport my experience has been that the airline doesn't ask for the PR card (once in Atlanta). This is risky because if they do ask your employee is SOL
This is the way to go if he has a US passport and there is absolutely nothing risky about it. A US passport-holder does not require a visa (or an equivalent, such as a PR card) to enter Canada.
He will have no problem at the check-in, but might face a minor delay at CIC at the port of entry.