I don't understand this reasoning. Isn't the definition of a "delay" that a flight departs or arrives after it is scheduled to? So if an airline has a flight that is consistently 15-minutes late, why is it so bad to then put an extra 15 minutes in the schedule, if that's what the actual time usually is? Wouldn't most travellers prefer to be told up front (i.e., in the published timetables) that a flight will arrive at 1715 instead of 1700? Just because a flight used to arrive at 1700 10 years ago, if today's schedule shows a 1715 arrival and that is when it arrives, how does that make it a hidden "delay?"

This is like saying taking the bus from DC to NY, even if the bus arrives according to its schedule, the bus actually has a "hidden delay" because some other mode of transportation could have been there sooner. Busses don't go as fast as planes, so it is not fair to compare the two; planes cannot get through congested airports as fast today as they could 10 years ago, so that is not a fair comparison either.