Just go to the airport. If you show up with in 2 hours, typically any airline will accommodate you on the next available flight. This is sometimes called the "flat tire rule," even though often it has nothing to do with car trouble. Don't go in to some crazy story, just tell the agent you missed your flight. They probably won't care why. I can't remember the last time an agent cared specifically why I missed my flight. You could mention the passport thing if you wanted, but again it doesn't really matter.

One thing to keep in mind is that loads are high, so there is a possibility that they will not be able to accommodate you until the next day if all flights are full and you don't make it on standby. If that happens, typically the airport will syncranize your e-ticket for the next days flight and not charge you a change fee or additional collection. This is at the agents discretion, but they can do it if they feel like doing it.

I would NOT call any airline about this. First, res agents typically do not have the discretion that the airport agents do, for instance, they would have to charge you the change fee plus fare difference to move your flight. Second, often times reservations will enter in a comment in a reservation saying what you were advised the policy is. E.g. that you were advised it is the change fee plus fare difference to change flights. This will make it more difficult for you when you naively show up at the airport having missed your flight.

I miss flights several times a year due to work, ground transportation (I live in BOS ) or sometimes because I buy the cheapest ticket at say 6:00 A.M. and go later. I would say 99% of the time I am able to get out the same day, and the worse thing thats ever happened to me is I have had to travel the next day which is sometimes a blessing as it gives you more time to pack, relax, etc.

It is really no big deal as long as you keep your cool, and just work it out at the airport.

The online check in suggestion is also a good one especially if you think you may be able to cut it close.

Finally odds are Fedex will deliver before 3, but that depends a bit on the route you have for Fedex delivery. But I would say its the exception at least for me to get the package right at the cut off time.

You'll of course also save time with no checked baggage to worry about.

Also the gate agents can rebook your mileage ticket for you even if the special class for awards is not available especially if its a same day thing.

If you really want to sort it out beforehand, go to the airport before your departure date and see if they will move you to a later flight. This can work too.

Whatever you do, don't call. I can fill pages of horror stories of what might happen to you if you call, so don't do it . Hint, it involves you paying a lot of extra money to the airlines.