U.S. Customs and Border Patrol (CBP) is encouraging international travelers to apply for Electronic System Travel Authorization (ESTA) as early as possible, but no later than 72 hours before they plan to travel to the United States. CBP says that changes in ESTA processing make same-day approvals unlikely.

ESTA is an automated system used to determine if a traveler poses a law enforcement or security risk. All international travelers who seek to enter the United States using the visa waiver program must apply for ESTA before travelling. Travelers flying to the United States under the visa waiver program will not be able to board their flights without an approved ESTA.

CBP suggests that international travelers apply for an ESTA at the time they book their flights or no later than three days prior to departing for the United States to minimize the risk of delays.