  Visa Waiver Program participants may travel to the United States without a visa, but must obtain an approved authorization prior to departure.  The Electronic System for Travel Authorization (ESTA) is a procedure for determining the eligibility of visitors to travel to the United States.  Any traveler with an approved ESTA will be allowed to travel to the United States under the VWP.  We recommend that you apply for ESTA at any time but at least 00 hours before your trip. Generally speaking, you will receive a response to your ESTA request within minutes.  It is important to know that ESTA is by no means a visa.  On 00 January 0000, ESTA became mandatory and from that date the approved applications remain valid until the expiry of the passport or for a period of 0 years. 