May 2, 2013

Unpacked: Air Traffic Control Programs

Welcome to Unpacked, where we demystify hot topics in the airline industry! This time we’re talking about a topic you likely heard a lot about in the past two weeks around the sequester, or FAA furloughs, Air Traffic Control.

Different types of Air Traffic Control (ATC) Programs

The National Airspace System (NAS) is one of the most complex systems in the world. There are more than 19,000 airports and 600 air traffic control facilities serving more than 50,000 flights daily. The Air Traffic Controllers are responsible for safely managing all this traffic.

When the normal flow of traffic into an airport is disrupted, it lowers the arrival rate, and forces delays in order to space the planes out.

The normal flow of traffic gets jammed up by weather, increases in the number of flights in and out of an airport, runway construction and maintenance on the navigation systems. With the recent furloughs, ATC delays were compounded with less eyes in the towers and air traffic centers to manage the traffic.

The three main types of ATC programs that cause flight delays are:

Ground Delay Programs (GDPs)
These are designed to limit ARRIVAL traffic into an airport. Each flight impacted is given an “EDCT” (pronounced “EDICT”) or “Wheels Up Time” to ensure they do not arrive until the destination airport can handle the traffic. Most of the time, GDPs impact short- and medium-haul flights the most. Transcon and international flights are rarely impacted by GDPs—by the time they land in the airport, the weather or situation can completely change. Typically, we know that when airports are in GDPs, there will also be holding, so flights bound for that airport are planned accordingly to hold for a while to avoid a diversion.

Ground Stops (GS)
This is a temporary measure to stop arrival traffic at an airport that can no longer accept traffic. Flights are held at the originating airports for the duration of the GS. No EDCTs are given until the GS is lifted. Often, Ground Stops turn into GDPs.

Airspace Flow Programs (AFP)
AFPs are designed to meter the amount of traffic through a particular area of the airspace. ATC uses these to space out the traffic in a particular center. Flights are given EDCTs just like in a Ground Delay Program, which ensure they pass through the affected area at a particular time. These can be very challenging to explain to customers—it can be perfectly sunny and fine in both the origin and destination, but the route goes through a particular center that is short-staffed or challenged by weather, so flights are spaced out.

Another common tactic ATC for terminal-issues may take is a departure stop, which stops traffic departing from one direction or from a particular airport. This is done often for example to stop LaGuardia or Newark departures in the New York area to allow Teterboro to depart. Another example of when ATC utilizes departure stops is when southbound departures are stopped out of JFK, but west-bound and north traffic continues. Typically, departure stops are used to handle weather-related challenges, but the staffing issues due to furloughs have put ATC in the position to issue departure stops to manage the traffic.

What is the “Arrival Rate” and how is it calculated?

An arrival rate is a measurement of how many aircraft a particular airport can accept in a given hour. Each airport’s  arrival rate can vary based on a number of factors, including the runway configuration it is in, the weather, the wind, etc. Each type of aircraft requires a different runway length for takeoff and landing, and this can also drive runway changes, if a big old plane has to come in and change the configuration for that flight to operate.

Airports typically have runways that run in different directions to allow them to respond to changes in the winds without completely shutting down. However, in congested areas like NYC, certain configurations at JFK or LGA or EWR can conflict with approaches for one of the other two airports. The Tracon and NY Center work to orchestrate these configurations daily to manage the many flights in and out of our hometown.

Why would the ATC Team issue these programs due to Staffing?

FAA furloughs made a system that is already complicated even more complex. By reducing staffing in the centers and tracons, there were simply fewer eyes to monitor the system. To safely keep flights scheduled, ATC had no choice but to space the flights out when staffing levels dip below minimums.

The way that the FAA implemented their furloughs made airports like NY, FLL, LAX, ORD, DEN, that are already heavily trafficked, particularly vulnerable to AFPs and GDPs due to FAA staffing. Essentially, they implemented across-the-board cuts that reduced staffing at an equal rate at every facility. The previously named Tracons, Centers and towers already were understaffed, so the cuts made the situation even more challenging. At the same time, places with less air traffic, and lower flight volume, weren’t seeing an impact due to these delays.

The FAA furloughs caused a combination of GDPs and AFPs used to meter traffic in light of the FAA furloughs. Our Air Traffic System Controller team communicates daily with the FAA, the A4A and other airlines to understand their plans for the day. All of us rely on this team to keep us posted on what’s coming in the rapidly changing environment post-FAA furloughs.

How do we post ATC delays?

We aim to reduce delays to two or less hours by swapping aircraft or working with the FAA to improve efficiency. When needed, we make the difficult decision to cancel flights to help reduce volume and keep other flights running on time with fewer delays.

Because ATC delays tend to change rapidly based on weather, we often post only a portion of the ATC delay. Remember though, once we post one delay, we end up delaying a whole line of flying. Each plane has lots of places to go and customers to transport each day. That EWR-TPA flight delay could end up disrupting TPA-DCA and DCA-SJU flying later in the day. That’s when the system operations ninjas get to work and see if we can swap to different aircraft or move things around to eliminate the down-line impact of delays.

Why did we cancel flights due to ATC delays and how do we choose the flights to cancel?

When flight delays due to ATC initiatives became excessive, and there were no other options to recover (such as swapping aircraft), the system operation center looked for strategic flights to cancel to relieve the volume in an airport and reduce delays.

In slot-controlled airports like the NY Metros, each flight is pre-assigned an arrival time. When that time is delayed due to a GDP or AFP, we can sometimes improve delays across all our flights by cherry-picking a handful of flights to cancel, and then substituting later flights on to earlier slots that are now delayed.

When we chose flights to cancel, they were based on the time of the projected ATC impact, the flight load and market (we don’t like to cancel one-flight-a-day markets, for instance). Our team works with the Air Traffic System Controllers to determine which slot substitutions will reduce the most system delays and relieve delays across the system.

The highways of the sky

A key part of the System Operations team is our ATC Coordinator team, led by Bill Cranor, Director Air Traffic Services. ATC Coordinators closely monitor departure and arrival rates at key airports and work with Air Traffic Control and the other carriers to keep our airline on time. However, the cards we’re dealt in this airspace tend to make ground delays and other traffic management initiatives inevitable.

It’s easy on a crazy weather day with snow or thunderstorms to explain why a flight is delayed. It gets much trickier on a day when it’s sunny in Newark, say and sunny in Tampa and yet, still, the flight is delayed.

Think of the airspace on a good day as a four-lane highway. Everything is running smoothly. Then, you can compare the airspace on a bad weather day to a day of heavy road construction. Suddenly four lanes are reduced to one and the traffic gets backed up and bottle-necked as everyone merges to that one lane. That’s what happens when a ground delay program or ground stop goes into effect. Basically, ATC is bottle-necking the planes to keep them all safe.

As Bill is quick to point out, “Planes aren’t like cars—once they get going, they can’t back up and they can’t stop.” While that’s an option on the Belt Parkway, we can’t very well make that our plan and just take off and hope the traffic works out. We just have to let it ride.

Check out our previous editions of Unpacked and stay tuned for the next up!

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