原来叫预查（preclearance）不是飞地，主权还在^_^

The following Canadian airports have U.S. preclearance facilities, meaning travelers can clear U.S. customs and immigration before boarding their flight to the U.S.: Calgary, Edmonton, Halifax, Montreal, Ottawa, Toronto (Pearson), Vancouver, and Winnipeg. 

 

Here's a more detailed list: 

 

• Calgary International Airport
• Edmonton International Airport
• Halifax Stanfield International Airport
• Montréal–Trudeau International Airport
• Ottawa Macdonald–Cartier International Airport
• Toronto Pearson International Airport
• Vancouver International Airport
• Winnipeg James Armstrong Richardson International Airport