Two stories from a few years ago using Celebrity Air.
Turns out our booking to Barcelona was a group booking with two other couples we did not know. With great difficulty, I managed to get into the booking with the airline. We all had been assigned to the back row of the plane aka seats wouldn't go back. I changed out seats. Had gotten the names of the other 2 couples. Did some research and found the phone number of one. Gave them a call. Explained that we were on the same same cruise & plane booking and the issue with seating. They knew the other couple as well. They were then able to change their seats, too. If I hadn't been able to get the seat assignments, we would have had a very uncomfortable flight.
Another time, our return flights was cancelled but only the cruise line was notified, not us. When we got to the airport, we were told that the notification had gone out a week before to the cruise line. Luckily, they found a flight leaving shortly with a connection through SF to get us back to JFK. We had to rush through customs -immigration to make the flight.