Beware. The later flight option isn't what it's made to be.
It's really means next flight out.
For starters, you have to be at the airport within two hours of your original flights departure time. You will then be confirmed on the next available flight. No if's and's or but's.
Well the one expception. I was able to get second flight out when I needed time to go back to my vehicle to get luggage.
This isn't much of a benefit if you want a later flight on a route with frequent service.