Preclearance
Preclearance allows U.S.-bound air passengers to get advance approval to enter the United States from established locations in airports outside the country.
If you have questions regarding preclearance and border crossing procedures, you can contact the CBP office at the U.S. Embassy in Ottawa. They can be reached at 613-523-8120, and can be reached Monday to Friday from 8:30 am to 5 pm.