Visiting from Outside the USA?
If you are coming to our convention from outside of the USA, and you will be traveling on the Visa Waiver scheme, you now need an additional travel authorization. Basically you need to register your intention to travel with US Customs & Border Protection. The idea is to cut down on the number of false positives when they get name matches with the no-fly list. This way they can check who you are in advance. Note that this does not give you permission to enter the USA. You still have to go through the usual immigration checks. But without this “ESTA” authorization you may be told you cannot board the aircraft.
If you Google ESTA you will find several companies offering to handle the process for you for a fee. These are scams. You can get the authorization for free from this US government web site. The application process is very simple and you should an answer back within a few days at most.