Originally Posted by
fastair
I believe you are only allowed to use your nexus card to bypass WHTI (Western Hemisphere travel initiative, an agreement that requires a passport for air/sea border crossings) to cities that have a us CBP presence (preclear airports) there. If I were your gate agent, and you were going to Regina, Saskatoon, or the other non-preclear airports, you might not be flying. YQB isn't a preclear, but I'm not sure if it is a WHTI waived city (or as the link I will post calls them, "designated Canadian airport".)
So Nexus is nice, but there are other rules that may require a passport. http://www.cbp.gov/travel/us-citizen...ram-background note thT returning from Canada, it says nexus OK, IF traveling from an approved airport. I realize that it applies to the US, not the other way around, but there are nuances that COULD make departing to these places on the outbound of a round trip difficult.
AFAIK, a Nexus card is only approved as a WHTI-compliant document for air travel when used at a Kiosk. That said, the kiosk doesn't work, or you are sent to secondary, and asked for your passport, then you are basically SOL. The question comes up in the Nexus info. thread constantly if you can travel on a Nexus card without ones passport. Sure, it's theoretically possible to do it. But I would never, ever put my Nexus at risk for this - my passport can stay in my pocket if it isn't needed, and I have it if it is.
As for GAs, I find most will not accept a Nexus card anyway. So rather than try and explain, etc., I find it's far easier to just use show my passport at the gate. GAs all know what it is and is always checked in seconds.