As of October 24, 2005, USA legislation requires that airlines collect more personal details on passengers traveling to the USA.
This additional information will need to be requested when passengers check in, which may cause longer waits. E-ticket passengers can enter the additional information from the convenience of their homes via Internet check-in. Click here for more information.
Internet check-in is available between 30 hours and 1 hour prior to the departure of your flight. For KLM flights to the US and for flights being operated by Northwest Airlines from Amsterdam, Rome, Frankfurt and Bombay, Internet check-in is possible only between 24 hours and 1 hour prior to the departure of your flight
If you are traveling to the US but you have no e-ticket number, you cannot check in online. You can, however, make use of this API form (Advanced Passenger Information form) to collect the required information ahead of time.