If you have a passport from one of these countries which was issued after 2001, you must use the Electronic System for Travel Authorization to apply for an electronic authorisation whenever you travel to the United States of America.
To obtain it just go the website and complete the form. This process must be carried out at least three days prior to travel. However, and to prevent any setbacks, you can request this authorisation before booking the trip.
Since 20 March 2010, airlines that allow passengers to travel to the USA without authorisation are also penalised.
TAP reserves the right, as of that date, to refuse to allow passengers to board until they have completed the necessary formalities.
Procedure:
- Go to the Electronic System for Travel Authorization website and enter the basic identification.
- When your travel has been authorised, print the document and keep it with your passport. You must show it on request when leaving Portugal or at US border control.
- If the system replies “Travel not authorised”, you will have to apply for a non-immigrant visa at the nearest US consulate or the US Embassy in Lisbon.
- If the system replies "Pending authorisation" you must return to the website 72 hours later to get the final answer.
- These authorisations are valid for 2 years from the date they are obtained and for multiple entries into the USA. If your passport expires, you must request a new authorisation.
More information available at:
U.S. Embassy in Portugal - Visas to the USA.
U.S. Government - Visa Waiver Program