A Transit ESTA for USA is required for eligible travellers from Visa Waiver Program (VWP) countries who are passing through the United States on their way to another destination. Even if you do not plan to leave the airport, you generally need an approved ESTA because the U.S. does not have an international transit zone like many other countries. The application is completed online by providing your passport details, travel information, and answering security questions. It is recommended to apply at least 72 hours before departure, although applying earlier is always the safer option. Make sure your passport is valid, your travel details are accurate, and you have confirmed onward travel. An approved ESTA allows transit stays of up to 90 days under the Visa Waiver Program, provided you meet all entry requirements.