Originally Posted by
jrl767
the advantage of being on the 6am, of course, is that when your SDC window opens at T-24 you have 18 hours' worth of options in front of you
(this is why I often book the 1240am SEA-MSP-WAS)
I don't understand your comment. Regardless of your original flight time, you can SDC onto any flight on the same day, 24 hours worth of flights. People on an early flight can telephone earlier, so they may have some advantage in grabbing seats, but otherwise the rules are the same. In particular, one can SDC to earlier or later flights.