Air France and British Airways soon grounded all Concordes indefinitely, revoking their certificates of airworthiness. The next flight was fully booked, but the agent would be able to get you on the one six hours hence. Oh, there were terrible thunderstorms. And there was that labor problem with United Airlines. Planes are packed.
Schedules are tight.
Any delay ricochets from airport to airport, airline to airline, throughout the system, until nothing functions as planned. The way the reading light focused on your knees. The yogurt that spurted on your neighbor as you opened it. Fly early in the day and build extra time into your schedule. Know ahead of time the departure time and airline for the next couple of flights to your destination.