Sorry to bump up an older thread, but I was truly unsure of the proper thread for my question.

My cousin just booked a ticket EWR-YYZ-CLE on the outbound (used Expedia) UA to YYZ and AC to CLE and then called me (I am resident travel guru in the family) to inquire how Immigration and Customs would work in Canada (and I guess the USA though he is a USA citizen so they really cannot deny him access to the USA) as he is connecting in Canada to fly what is essentially a domestic ticket.

He stumped me as I never even considered nor experienced such an itinerary in my life, so I am going to the real experts FTers for the answer.

Is my cousin able to stay in transit or must he clear Canadian Immigrations and Customs and then USA Immigration and Customs before boarding his flight to CLE?

Thanks,
Dan