If your trips have two different confirmation numbers, then missing one flight will have no affect on the other. If they are on the same confirmation, then missing the outbound causes the return to also cancel. If you miss a flight, then you forfeit funds paid for that trip. If you know you are going to miss a one way flight, be sure to cancel no less than 10 minutes before departure time, and you'll at least receive travel funds. You can do this yourself, or you can contact the airline. If you are going to miss the outbound of RT , cancel the outbound to preserve the return flight. You'll have to do this via phone or perhaps the cell phone app. You can't do this yourself. If you'e already missed your flight, you have some hope. The airline knows that people get delayed. Show up at the airport and you'll be able to try to travel standby. If you can't get to the airport (you had a wreck and can't use your car, for example), call the airline or use the cell app ASAP. I'm not sure what would happen in this case, but it's worth the try.
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