|Quoting Go3Team (Reply 8):
I just tried checking online for I flight I have on US tomorrow, and the damn thing said I can't. US flight bought thru US itself.
Is it an international flight? Are you traveling with any lap-children? Are you traveling in a party of more than eight passengers? If so, you cannot check in online. The only exception is that select international destinations (they probably mean Canada and places with pre-clearance but I'm not sure) can still use online check-in.
One other thing from the website: "Please Note: Due to heightened security some customers may not be able to check-in online." Do you regularly have to go through secondary security screening (not at random) or have the agents ever had your name come up on the no-fly list and had to verify that you were not the individual in question? Then you also can't check in online.
Sorry for all the edits, but I keep finding more info! If your flight is tomorrow but still more than 24 hours from now, you can't check in online. The flight also has to be on an e-ticket, not a paper ticket.
[Edited 2006-10-06 07:09:23]
[Edited 2006-10-06 07:11:06]