Originally Posted by
BigFlyer
The best practice is to check in with the airline using the passport of your
destination country. It is that passport that the airline uses to determine if you have proper documentation to enter the destination country and to board the aircraft.
Here is what
https://klm.traveldoc.aero/ says:
Passengers who hold dual nationality with Canada must use a Canadian passport to travel to or transit through Canada. Passengers travelling to or from a country that requires them to use the passport issued by its own government must carry both passports when travelling. This does not apply to American-Canadian dual citizens travelling to Canada and holding a passport issued by the United States, provided they also hold identification that shows their Canadian citizenship.
This makes sense and suggests that my "Option 3" is the way to go.
But the concern is this:
When the passenger leaves the US with the CA passport, the airline will provide the record to CBP, who will be unable to match it with an arrival record into the US. Would that be a problem?
It might be useful to mention that the passenger is in Global Entry and already listed both his US and CA passports in his GE profile so CBP can probably determine that a departing CA citizen is also a US citizen.