Last year we had ADRs for our arrival night at 1900 Park fare. Our flight was supposed to take off at around noonish, but got DELAYED for just over 3 hours! My DH wass calling the GF to talk to someone at 1900 PF, the dining line, but they wouldn't/couldn't do anything for us and said they were totally booked. Our ADR was for 5:50 and we didn't land at MCO until 5:40! I was most upset that I thought our girls were going to miss their chance of dining with Cindy and Prince Charming. However, when we arrived at the GF, we told concierge about missing our ADR and they helped us get in. We were able to be seated at 8:00 and proceeded to have a fabulous time.
The girls had been up since 6:45 that morning without a single snooze. You would never know it because just being in Disney gave them such a bolt of energy! It was such a great way to start our trip.
I would not schedule an ADR that required a credit card gaurantee or prepayment because of potential flight delays. But 1900 PF does not require either one, so it would most definitely be safe to book it and plan on going.