Originally Posted by
philfna
AndyTLe thanks for that info -- unfortunately there is more than a 3 hour difference between scheduled departure and the other flight I want to change to on that day.
That's fine. You just need to call 3 hours before your NEW flight. You could actually miss your original flight and then call to get the new flight. NOTE: If there is no availability on your later flight, you might be stuck in Y or completely SOL. However, that is typically unlikely. Most of that miss the earlier flight and take a later flight, will call the airline or use Seatcounter, EF, KVS etc to check on the number of seats available (to check on the liklihood of getting on the later flight).
If you do a search for "SDC" or "Same Day Confirmed" there are extensive posts on the ability (and the ease) of taking a later flight.
Example:
Original flight - 6:00 AM (you decide you want to sleep in and take the later flight)
New flight - 5:00 PM
Ability to SDC opens - 2:00 PM (if there is availability in your class of service, coach or first, you'll receive a Confirmed seat).