Happy New Year to everyone!
Yesterday, our return flight from Atlanta was delayed by half an hour, but we still landed at the scheduled time. . . . At first, I figured it was merely the usual sort of padding that airlines put into their schedules so that they can inflate their "on-time arrival" percentages, but half an hour is a lot of padding. Besides, if that were the entire explanation, there would be a lot of flights arriving half an hour early, which I can't ever remember happening.
So my working hypothesis is that the scheduled departure/arrival times are based on maximum fuel efficiency, the equivalent of driving at 55 mph. When the flight departure is delayed, however, the pilot flies at a faster, less fuel efficient speed, the equivalent of 90 mph. It burns more fuel, which is bad from the airline's point of view, but it helps maintain the flight schedule, reducing delays and traveler frustration, which is good from the airline's point of view.
Am I right about this?