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Do you have to complete the ESTA form even if you are just in transit?

Yes. Anyone who passes through US territory, even without staying there, needs to have an ESTA. Once you arrive in the US you will go through immigration and customs control, run by US border authorities. Your personal documents will be checked before you are allowed to proceed to your final destination.

So all travelers in transit must have the necessary travel documents, requested by the US authorities. You can indicate that you will be in transit in the online form for ESTA.

Exemple 1: Kim et Stéphane
Kim and Stéphane are a couple of artists who are particularly fascinated by Mexico. After a time of planning, they will leave for the journey of their dreams next month. They will make a stopover in Miami before arriving at their final destination in Mexico. Kim and Stéphane will only spend a few hours at the Miami airport, waiting for their flight to Mexico. Yet once they have arrived in Miami, they will have to go through immigration and customs control of the United States.

After receiving their email, our customer service confirmed to them that both must get ESTA before boarding their flight.

Exemple 2: Olivier
Last year, Olivier obtained his document online to travel to the United States; He went to Charlotte for a music festival. In the next few months Olivier will go to Bogotá, Colombia, to visit his daughter, who lives and works there. His flight stops in Atlanta. Olivier will be able to use the same ESTA he did to go to Charlotte, although this time it will only be in transit. Olivier can update the information on his ESTA (modification of the address in Charlotte, with a Transit status). But this update for ESTA is optional.