Forgive me if this is common knowledge outside of the USA, but I stumbled across a new program, designed by the Department of Homeland Security, for travellers.
This is irrelavent to anyone with a visa, but from January 12th, 2009, anyone wishing to board an aircraft to the United States under the Visa Waiver Program must first be pre-approved by the DHS.
Approval is available right now, is valid for up to two years and is currently free of charge. Airlines, apparently, will not allow anyone to board their aircraft after this date unless they have the pre-approval document in their possession.
The document *DOES NOT* guarantee right of entry into the USA - but does guarantee that you will not board the aircraft at your departure point without one.
Full details available at;
https://esta.cbp.dhs.gov/ and
https://esta.cbp.dhs.gov/esta/WebHel...ine_Help_1.htm
The first link is the application - the second is an FAQ sheet.
If you have anything to add to this - there's an "open" thread in Professional Training forum.