As of 1st August 2008, a new online system is available for citizens and eligible nationals of Visa Waiver Program (VWP) countries to apply for advance authorization to travel to the United States.
Effective 12th January 2009, all VWP travelers will be required to obtain an electronic travel authorization prior to boarding a carrier to travel by air or sea to the U.S. under the VWP.
Applications may be submitted at any time prior to travel, however it is recommended that applications are submitted no less than 72 hours prior to travel. In most cases you will receive a response within seconds.
In cases where authorization is denied, it is strongly recommended that a non-immigrant visa is obtained at a US Embassy or Consulate before arriving at the airport.
Find out more and apply online