One curiosity on the Canada–U.S. border is the presence of six airports that straddle the borderline. The airports were built prior to the U.S. entry into World War II as a way to legally transfer U.S-built aircraft such as the Lockheed Hudson to Canada under the provisions of the Lend-Lease Act. In the interest of maintaining neutrality, U.S. military pilots were forbidden to deliver combat aircraft to Canada. The aircraft were flown to the border, landed, and then at night towed on their wheels over the border by tractors or horses. The next day the planes were crewed by RCAF pilots and flown to other locations, typically airbases in Eastern Canada, from where they were often flown to the United Kingdom and deployed in the Battle of the Atlantic.
Piney Pinecreek Border Airport is located in Manitoba and Minnesota. The northwest/southeast-oriented runway straddles the border, and there are two ramps; one in the U.S. and one in Canada. The airport is jointly owned by the Minnesota Department of Transportation and the local government of Piney, Manitoba. It is assigned U.S. identifier 48Y and Canadian identifier JX2.
International Peace Garden Airport is located in Manitoba and North Dakota adjacent to the International Peace Garden. The runway is entirely within North Dakota, but a ramp extends across the border to allow aircraft to access Canadian customs. While not jointly owned, it is operated as an international facility for customs clearance as part of the International Peace Garden.
Coronach/Scobey Border Station Airport is located in Saskatchewan and Montana. The east–west runway is sited exactly on the border. The airport is jointly owned by the Canadian and U.S. governments and is assigned U.S. identifier 8U3 and Canadian identifier CKK3.
Coutts/Ross International Airport is located in Alberta and Montana. Like Coronach/Scobey, the east–west runway is sited exactly on the border. It is owned entirely by the Montana Aeronautics Division. It is assigned U.S. identifier 7S8 and Canadian identifier CEP4.
Whetstone International Airport or Del Bonita/Whetstone International Airport is located in Alberta and Montana, and similarly has an east–west runway sited exactly on the border. It is assigned U.S. identifier H28 and Canadian identifier CEQ4.
Avey Field State Airport is located in Washington and British Columbia. The privately owned airfield is mostly in the U.S., but several hundred feet of the north-south runway extend into Canada, and both Canadian and U.S. customs are available. It is assigned U.S. identifier 69S but does not have a Canadian identifier.
https://en.wikipedia.org/wiki/Canada%E2%80%93United_States_border#Cross-border_airports
