Though US border Pre-clearance isn’t necessarily open for all flights due to the hours it’s open, the following Canadian airports operate U.S. preclearance facilities:
- Calgary International Airport / YYC
- Edmonton International Airport / YEG
- Halifax Stanfield International Airport / YHZ
- Montréal Pierre Elliott Trudeau International Airport / YUL
- Ottawa Macdonald-Cartier International Airport / YOW
- Toronto Pearson International Airport / YYZ
- Vancouver International Airport / YVR
- Winnipeg James Armstrong Richardson International Airport / YWG
Practically, this means allowing sufficient time to complete immigration and customs formalities before you fly. Though checked baggage generally isn’t required to be present, USCBP has photos, etc. of your baggage and you do process customs.
When your flight arrives in the US, it will generally arrive as a domestic flight and passengers and their checked baggage arrive as domestic.