Travelers entering the United States under the Visa Waiver Program by air or sea must have an approved travel authorization (ESTA), which has been a requirement since January 12, 2009. After you have applied and received your travel authorization number, you may update specific information before each U.S. entry. You can update your ESTA multiple times, but you should not apply for a new ESTA unless you have a new passport, the circumstances around your Visa Waiver eligibility has changed, http://kurose96.or.tv/link3/link3.cgi?mode=cnt&hp=https://estatousa.com/esta-employment-information/ or your current ESTA has expired. Travel authorizations are generally valid for two years. Each traveler with an approved travel authorization can update it online. It is recommended to confirm the status before purchasing any airline tickets to ensure that the current ESTA is still valid.