Anyone who has travelled with any sort of regularity knows flight delays happen. They happen for many reasons; mechanical, operations, customer service issues, and weather - either at the airport, destination airport, or somewhere in between. So when your flight is delayed, a logical question to ask is: "When should I leave for the airport?" Answer: In most cases, you should arrive as if departing during the initially scheduled departure time.
The reason is pretty simple: Delays can un-happen. A last minute plane swap or an alternate flight path during inclement weather are ways to reverse anticipated flight delays. For instance, a flight I was on last year was expected to be nearly two hours late for departure due to building thunderstorms. Suddenly, the airline began paging all passengers in the terminal to immediately board the flight - it was leaving 15 minutes early, to avoid the storms. (Way to go Southwest Airlines!)
The reason is pretty simple: Delays can un-happen. A last minute plane swap or an alternate flight path during inclement weather are ways to reverse anticipated flight delays. For instance, a flight I was on last year was expected to be nearly two hours late for departure due to building thunderstorms. Suddenly, the airline began paging all passengers in the terminal to immediately board the flight - it was leaving 15 minutes early, to avoid the storms. (Way to go Southwest Airlines!)
Too often of course, when the airline says the flight is delayed... it will be delayed. But occasionally there are instances where they can "fix" the problem and leave on time. Therefore, it is highly recommended you arrive at the airport ready during the initial time of departure - unless of course the airline recommends otherwise.