I was scheduled to fly DEN-ORD-BUF during the holidays a few years ago. ORD was a mess, all the DEN-ORD flights were overbooked. My flight kept getting delayed more and more, and it got to the point where I was going to miss the last connection out of ORD.

I talked an agent into putting me on the non-stop AC DEN-YYZ after showing my passport, and very nicely explaining that this would free up a seat for someone trying to get to ORD, and allow me to get to my destination that evening.

Trying to route DEN-YYZ-IAD or similar would be a much harder sell though. I've tried to route DEN-YVR-HNL in the past, and that doesn't work.