Clients are responsible for having valid travel documents when they travel. They will need to present a valid passport to check-in, to pass through security, and to go on board the aircraft. We recommend to print out the itinerary and to take it with you to the airport. Some nationalities require a visa for Mexico, see our section about visa. If clients are non-US Citizens and they are traveling through the USA, even if it´s only a layover, they will need authorization to enter the USA. Citizens or eligible nationals of a Visa Waiver Program country have to apply for ESTA (Electronic System for Travel Authorization). Please go to the following link for more information: https://esta.cbp.dhs.gov/esta/.