ESTA registration is required for all travelers to the United States under the Visa Waiver Program. There is a US$14 fee for ESTA registration. The fee can be paid online using any of the following credit cards: Visa, MasterCard, American Express, or Discover. Third parties (travel agents, family members, etc.) can pay your ESTA fee for you if you do not have the correct type of credit card. If the ESTA registration is denied, the fee is only US$4.
If a traveler’s main reason for being in a country is simply to pass through en route to another final destination, the country may issue a transit visa. For example, Australia issues transit visas for stays up to 72 hours for people in transit and for crew members arriving to work on flight or ocean vessels. Most countries do not require visas for travelers who arrive to change planes but never leave the secure airport areas. However, a more restrictive kind of visa called an airside transit visa is required by some countries even for travelers who remain in the airport.
^ Encompasses Schengen member states - Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden and Switzerland as well as Bulgaria, Croatia, Cyprus and Romania and countries without border controls - Monaco, San Marino, Vatican and a country accessible only via Schengen area - Andorra.