Originally Posted by
joejones
At least in the US, while there is no separate passport control check upon departure, the government is still collecting passenger manifests from the airlines to see who is leaving the country when, so if you enter on one passport and leave on another, it can certainly appear (to the government) that you overstayed.
I agree that they collect and process airline manifests, but the system is not and cannot be a surrogate for proper exit controls. A case in point; a good friend of mine, who lives in Europe, regularly travels to the US on his Canadian passport, and leaves on his British one. Has never had any issues. I do remember that I-94 passenger had to, for a while in the early 2000s, register their exit at a kiosk. That system didn't last very long.