Eligible citizens or passport holders of any Visa Waiver Program country require either a visa or an ESTA travel authorization to travel to or transit the United States of America. If you are only planning to transit to another country, without remaining in the US, answer “Yes” to the “Is your travel to the US occurring in transit to another country?” question, part of the ESTA online application. However, the “In Transit” does not refer to layover flight where travelers are not allowed to leave the airport.
Please note that an ESTA travel authorization is valid for 2 years. It does not limit the number of times you can enter the country as long as you are in transit. Moreover, note that if you answer that “YES,” your visa is a transit visa and you wish to reuse your ESTA to travel at a later date, it will no longer be valid.
When applying for an ESTA online, you link your current passport to the application for travel authorization. Should your passport expire and you are issued a new one, you will be required to apply for a new ESTA before your next trip to the United States. (if you want read more about the ESTA for transit, please follow the link)