Nobody likes weather delays when flying. Passengers hate them, the crew hates them. The airline hates them.
Some delays are pretty straight forward and obvious. A mechanical delay is pretty easy to understand. If the flux capacitor breaks, we need a new one before we start our flight. If a flight attendant gets injured, we need to get a replacement before leaving. (yes the FAA mandates a minimum number of flight attendants for flight)
Air traffic control delays come in two primary flavors. Traffic congestion and saturation resemble rush hour on a big city freeway. The road can only handle so many cars at one time. An airliner cannot just stop like a car, so air traffic control has to manage the number of “planes on the road.” An en-route delay involves managing the “planes on the road” situation. Airports can handle a certain number of arrival aircraft per hour. The maximum number of arrivals per hour relies on everything working. Everything, in this case, refers to things like runways, approach systems, and radar. Weather also plays a role in the number of arrivals handled in an hour. When the weather gets worse, and runways shut down the number of flights allowed in decreases.
The weather delay can be puzzling. Watching the snow pile up on your airplane makes the weather delay easy to understand. Your ride at the destination telling you about the massive hail falling also makes things clear. But your airplane is sitting in the sunshine. Your ride at the other end is lounging on the beach. How can there be a weather delay? What weather? Where? Sometimes the weather is between where you are and where you want to be. Why can’t we fly around the weather? Sometimes, the lines of weather are long. A flight from Chicago to Denver may go as far south as San Antonio to get around the weather. This is going to be a much longer flight than planned. It may be better to wait an hour for the weather to pass Chicago than to add hours to the trip.
What about when the area of bad weather is smaller? When this happens, air traffic control comes back into the picture. Let’s look at why.
Airplane freeways.
Airliners fly in controlled airspace. Many assume the pilot takes off and heads directly to the destination. In reality, the route flown consists of airways and navigational fixes. Air traffic control manages the traffic on these airways and between the fixes. The picture above shows high altitude airways in the northeast part of the United States. You can think of these airways as interstate highways for airplanes. The different altitudes provide “lanes” on these freeways. Let’s forget your mental picture of Interstate 80 near Casey, Iowa. Replace it with a mental image of Interstate 10 near downtown Los Angeles. Let’s make that on a Monday at 5:10pm. Yes, those airways are busy.
The picture above is a snapshot of air traffic over[opik;m. the United States. This is a Monday morning around 9am.
Back to our weather delay.
You are sitting in the terminal at Boston Logan Airport so ready for your spring break trip to Miami.
It is a bright sunny afternoon even if it is cold in Boston. Your friends arrived in Miami yesterday.
They text you a few minutes ago sending pictures of themselves on the sunny South Beach. You are jealous of them when you hear the announcement your flight is now delayed 3 hours for the weather. What’s happening?
There is a large area of strong thunderstorms over the Carolinas and Georgia. The weather moves in, and the storms grow. Air traffic control moves flights to airways clear of the storms. The storms shut down airway after airway. Think back to the picture of Interstate 10 downtown Los Angeles at rush hour. A colossal accident (in our case a thunderstorm) closes Interstate 10. Cars try to switch to the 91 freeway. It doesn’t take long before that gridlocks.
Ground stop
In air traffic control world, it is time for a technique called a ground stop. The ground stop can be for a destination airport or for an en-route region. In this case, it is for the en-route region of the southeast United States. Flights are still going to our destination of Miami. They are coming from places like San Juan and Houston not affected by the en-route storms. The ground stop is a big time out. Air traffic control is saying no one takes off if the flight plan goes through the area of bad weather. Airline dispatchers are busy trying to get your flight routed around the weather. The answer to the reroute will be no if air traffic control cannot handle the flight on the new route. This is often due to traffic demands.
When issuing a ground stop air traffic control provides an update time. Usually, the update time is one hour after the ground stop begins. This update time does not mean your flight will be able to go at the update time. The time puts the pilots and airlines on hold. It keeps them from pestering the air traffic controllers every 2 minutes. (picture kids asking mom and dad, “can we go?” “can we go yet?” “how about now?”) When the update time arrives, air traffic control looks at the situation. If weather and traffic still look bad, the controllers issue a new update time. (most likely another hour from now) One trick with the ground stop, it can end with no warning before the update time. This can cause your flight to board and depart in a hurry. This is why you should stay pretty close to the gate during a ground stop. Keep reading, the fun is only beginning.
Gentlemen (and ladies) start your engines.
When the ground stop ends, the fun begins. Air traffic control can release your flight immediately. This can cause a scramble to get ahead of other flights and be front of the line to depart as mentioned above. Another option is a more measured response. The proclamation to leave You may hear a pilot mention an “edict.” They are not referring to a proclamation. They are talking about an EDCT or expect departure clearance time. This is sometimes referred to as a “wheels up” time. It can follow a ground stop or almost any air traffic control delay. The term “wheels-up time” is a good description because an EDCT requires that you be lifting off at that time. If you are still at the gate or taxiing out during your EDCT, you have “missed your time.” This can cause anywhere from a short to very long additional delay. Pilots hate to miss an EDCT time as it will delay the passengers further. Once the flight receives an EDCT, the pilots will determine a time to push back from the gate. This will allow them to taxi and perform preflight checks in enough time to comply with the EDCT. Don’t make the mistake of thinking “they won’t leave without me” once this new push back time is announced.
Hopefully, this offers a little peek inside the flight delay situation. As complex as this sounds, it is only the beginning. If your head has not exploded already read Ask The Captain Many Moving Pieces. The article provides another look behind the scenes. It discusses reasons and decisions affecting flight delays. Had a delay you don’t understand? Feel free to comment below.