If you think about all of the things that have to come together for a flight to take off on time, it's impressive that airlines do so well. You need an airplane with all the required maintenance checks and updates completed even with normal wear and tear of critical components. You need pilots rated on that aircraft who have enough time left on the day before they are no longer allowed to fly. You need flight attendants who also have enough available time before they have to rest. You need all the assorted gate and ground crew to ready the aircraft after it lands and as it pulls out of the gate. You need catering to provide the food that people order and to load it while the plane is on the ground. You need an ATC slot at the airport you are departing from and flying to. And you need to do everything quickly so that the plane is in the air enough to make a profit because a parked airplane doesn't generate any revenue for the airline.

Any one of these things can cause a delay, and many of them the airline has no fault at all in it (such as a thunderstorm closing an airfield down). But they have to absorb the effects and minimize the ripple across other flights whenever something does happen.

I think it would be interesting to visit the operations center of a major airline just to watch it come together as things come up.