When departing the US internationally, you can do so from any airport, even if it is not a CBP Airport.

If you are departing from a non-CBP airport, when you file the eAPIS the airport code will not be listed in the table provided by the system.

You will have to use the code of the CBP airport nearest to the departure site.

In the section "Actual Departure Location Description", describe the actual place from which the aircraft will depart. The "City" field should be the actual city from which the aircraft is departing.

After you submit your eAPIS, you will receive a departure clearance email from CBP. DO NOT depart if you have not received the clearance email.

If your plans change, make sure that you inform the CBP port associated with your departure. These changes must be coordinated with CBP, even if it is a simple time change.

Quote
For example, if your departure is approved for noon, don’t depart at 07:00 am or 10:30 am or 13:00 pm without explicit approval
from the CBP port.

Source: CBP Qquick Tips - June 2022

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