The Department of Homeland Security and the United States Customs and Border Protection have provided a secure website ESTA with an automatic form for you or third parties to complete and request a travel authorization. Once you enter the required biographical, travel, and payment information on the secure ESTA, the system will process your ESTA application to determine if you are eligible to travel to the United States under the Visa Waiver Program without a visa. The system will provide an automatic response and before boarding, an operator will verify electronically with the United States Customs and Border Protection that has a registered approved travel authorization.
The Electronic System for Travel Authorization (ESTA) is an automatic system used to determine the visitor eligibility to travel to the United States under the Visa Waiver Program (VWP) and whether said trip represents a security risk or a threat to public order.
USA ESTA approval authorizes a traveler to board a plane to travel to the United States under the VWP. Private airlines must be subscribed airlines of Visa Waiver Program. You can see the list of subscribed airlines. Though CBP recommends that you request it at least 72 hours before traveling, you can request it at any time before boarding. In most cases, you will receive a response immediately after submitting your application.