Thursday, November 1, 2012

How Airlines Get Back on Track After Sandy

How Airlines Get Back on Track After Sandy:

In this Wednesday, Aug. 1 2012 photo, a Delta Air Lines ramp agent assists a pilot as he pulls into a gate at JFK International airport in New York. Photo: Mary Altaffer / AP

Airports directly affected by superstorm Sandy are slowly getting back up to speed, and stranded passengers, airplanes and crews around the country are once again on the move.
Sandy forced the closure of several major airports throughout the northeast, leading to canceled flights around the world. According to, there have been nearly 20,000 flights cancellations in the United States this week. The airports serving Washington D.C., Philadelphia, New York, and Boston account for nearly half of those cancellations, but because those cities typically account for a large portion of overall air traffic on a normal day, airports as far away as San Diego and Seattle have been affected as flights to the northeast had no where to go.
The airports outside the hardest hit parts of the northeast resumed flights on Tuesday. In New York, John F. Kennedy airport and Newark began accepting arrivals yesterday, and are expected to approach normal operations today. New York’s LaGuardia Airport finally opened this morning.
Unfortunately for the thousands of stranded passengers, the complex nature of a very full system means it’s going to be several days for airlines to return to normalcy, according to Lance Sherry, a professor of systems engineering at George Mason University and director of the school’s Center for Air Transportation Systems Research.
“It’s a network of networks,” Sherry told Wired, “and the agents who make decisions are autonomous, distributed and adaptable.”
Sherry points out that on a normal day there is an amazing choreography between the various networks to deliver a passenger to their destination. The first problem facing airlines this week is where to park their planes. Before Sandy even got close to the northeast, airlines were flying their wares out of the path and parking them at airports with better weather, usually where ever they last delivered passengers. But difficulties arose for airlines that use affected airports as a major hub.
If an airplane flew from New York to Sacramento flight on Sunday, it would normally be flying back to New York that same day. This week it was stuck in Sacramento along with the passengers, pilots and flight attendants who were hoping to be back in the Big Apple. And because there are no airplanes in New York, the passengers at JFK and LaGuardia are stranded even if the weather improves – there are no airplanes or flight crews to take them anywhere.
Adding to the airplane shuffle challenge is the basic air traffic control and airport infrastructure that dictates how many airplanes can come and go at a given airport and around the country.

A gate at New York’s LaGuardia airport Tuesday. Photo: JetBlue
Like the flood waters draining off the tarmac, the rate at which the airplanes can flow back into affected airports may depend on the size of the bottle neck. At larger airports  with several runways – like JFK – it’s possible for air traffic controllers to work with pilots to land multiple airplanes at the same time, but the weather has to cooperate to use runways in close proximity or aligned in different directions. At smaller airports with just one or two runways, the valve can’t be opened quite as far and it will take longer for all of the airplanes to return.
Airlines and air traffic controllers must also balance the rates at which airplanes to return with the capacity of the airport. Land too many planes in short succession and where do you park plans – and where do all the passengers go? It’s a highly choreographed affair that controllers, airlines and crews on the ground have to balance. At JFK yesterday, the focus was on getting airplanes and crews back to New York, so issues with passengers were largely non-existant.
As those complex networks within networks begin to return to normal today and tomorrow, Sherry says the next biggest challenge to relieving the backlog of passengers is simply the physical space available on the individual aircraft.
“In the past five years the percentage of passengers on a given flight has gone up from the mid 60s, low 70s,” Sherry says of the airline’s load factor. “On the more popular routes, [it's] as high as 90 percent.”
That means that when a flight with 180 passengers is cancelled on a typical day, each subsequent flight to the same destination will on average only have space for 18 of those stranded passengers. The higher load factors is great news for the airlines because it means more seats are sold on a given flight. But it’s bad news when your flight is cancelled. And it’s especially bad news when thousands of flights are cancelled all at once.
Assuming that many of the stranded passengers in the wake of Sandy no longer need to get to their destinations and will choose not to travel, the delays are still going to last through the weekend and into early next week.

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