If you know that you require an Electronic System for Travel Authorization (ESTA) to board a flight to the U.S., it's always best to apply for an ESTAExternal site which may not meet accessibility guidelines and/or language preferences. as early as possible, and no later than 72 hours before your trip. This will ensure that you have all the documents you need to board your flight.
Not sure if you need an ESTA? Visit the U.S. Customs and Border ProtectionExternal site which may not meet accessibility guidelines and/or language preferences. website to find out.