The Visa Waiver Programme or VYP is a system in the US which allows citizens living in certain countries to visit the USA for a period of 90 days or less without the requirement for a Visa. There are certain restricted activities for the traveler but travel will be permitted for most holiday and business purposes. Citizens of none VYP countries will need to apply for a Visa in order to be eligible to visit the US. A list of the VYP countries can be found online.
You must apply through the Electronic System for Travel Authorisation or ESTA to determine whether you would be eligible for travel under this programme. You do not have to apply via ESTA for every trip that you make to the USA as your ESTA will be valid for 2 years. Normally you would need to make application at least 72 hours before you travel to ensure that processing has been completed, processing is normally completed much more quickly than this but it is recommended that you leave enough time in the event of delays or queries. If you visit the US regularly and never know when your visit may next take place, you would be advised to apply for an ESTA ahead of your trip whether or not you have any travel arrangements. If you want to learn more about this process head over to EVISUMSERVICE.
The 9/11 attacks prompted the US to consider their security more closely and it was as a result of the atrocity in 2001 that the ESTA system was brought into force.
The US welcomes many millions of tourists and visitors each year and wishes to continue to do so but wished to do so safely. The awareness of the need for an extra layer of security to allow them to be able to vet travellers resulted in the ESTA system. The US use the ESTA system to filter out as many undesirable travellers as they can.
After applying through the ESTA system, you will either be granted clearance or you could be refused.
It may also be that further checks may be required and they would mean your application may take longer to be processed. You will, however, be informed of the status of your application as quickly as possible. If your application is denied, you may still apply for a Visa to visit the US but this process can be lengthy so if you plan to travel to the US, it is always advisable to apply for an ESTA as soon as you can. You must make an application for your ESTA online.
If you fail to apply for an ESTA and go ahead and try to travel to the US anyway, you could be denied boarding rights on the aircraft and you would not be able to clear immigration.
It is a strict requirement for visitors to the US and no exceptions can be made. If you have failed to make application at the point of almost boarding, you must do so immediately and hope that your application will be approved instantly, often applications can be processed extremely quickly.