We all associate airports with waiting and delay. A nontrivial part of that delay at some busy airports is sitting on a plane that creeps toward along a taxiway for a chance to use the runway. The Wall Street Journal reports that the Federal Aviation Administration has implemented a new way of managing that line at New York’s John F. Kennedy airport — one of the nation’s most delay prone (At JFK, More Flying, Less Waiting on the Tarmac, Jul 29). Here’s how it works:
Now, airlines file flight plans with the Federal Aviation Administration indicating what time they want to take off. A metering program compiles requests, and takeoffs are scheduled in 15-minute blocks of time. Airplanes don’t leave the gate until their assigned time. And as a result, the conga line of 40 jets lined up at the end of a runway has been reduced to six to eight. …
Despite the simplicity of the restaurant-reservation idea, it took a major effort to put the metering system in place. While the system uses sophisticated software and an elaborate communications network linking airlines with airport schedulers, making reservations is still mostly a manual process. Like the best maitre d’, schedulers have to know the local market and know their customers. They study weather forecasts, flight paths and other factors to design the best order for takeoffs to maximize efficiency and accommodate requests and preferences from airlines. …
Mr. Stebbins and Ms. Farrell take the prediction and assign flights and estimated taxi time. If airlines don’t like the assigned time, they can ask for a change through the computer system, or chat online with the schedulers to resolve problems. Carriers can switch flights if they want to favor a departure with VIPs or lots of connecting passengers onboard, or give a plane undergoing mechanical repair more time before losing its reservation. They can even trade reservation times with other airlines.
For airlines, the system requires more intensive planning. Since departures may sit at gates longer, schedules have to be adjusted so that arriving flights don’t sit waiting for the gate to open up.
The pay off to this has at some level been modest. Delays, on average, have fallen only a few minutes. (The article also mentions that really long delays have also fallen dramatically. However, it fails to note that the Feds have also imposed big fines for leaving passengers trapped in planes for really long times.) To some extent modest gains aren’t too surprising. Runway times is a the binding constraint and this metering system doesn’t expand that capacity. (The exception to that is when wind changes force a shift to a different runway. That is quicker and wastes less capacity with 8 planes as opposed to 40.) From a queuing perspective, this scheme alters the arrival pattern to the server. It smooths out arrivals, reducing variability and hence delay. The benefits from reducing variability appear to be swamped by the fact that the system is very heavily utilized.
There are still real benefits for both passengers and airlines. These come from changing the experience of the wait and providing greater control. Passengers get to wait in the terminal as opposed to on the tarmac which most would prefer. (There is a question of how this is explained. If I am in a plane inching down the taxiway, I can see why we are running late. If the plane is 20 minutes late in boarding, I don’t necessarily know why or whether this is built into the schedule.) For airlines, they don’t burn fuel while planes taxi, which obviously saves money. They also get to pick and choose how to allocate delay. I suspect that could be very helpful. Everyone knows that planes are going to be delayed. Now airlines get to decide who is going to take one for the team. That is probably bad news if you are on the flight the airline decides to put at the back of the line, but at least lets someone think about how delay is allocated as opposed to spreading it around randomly.