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Weather and Flight Cancellations

© Courtesy of NOOA National Weather Service
A behind-the-scenes at what happens when weather causes flight cancellations.

You've just finished packing for this morning's departure to a crucial meeting in Chicago when your smartphone pings with an alert from your airline: Your flight has been delayed—or worse, canceled—due to bad weather.

Weather-related schedule disruptions can turn a routine business trip into an annoyance (a short delay), a major aggravation (a long delay) or a logistical catastrophe (a cancellation). With airline load factors topping 80 percent, finding an empty seat on another flight can be problematic; so for many business travelers, a canceled flight means a canceled trip.

According to Department of Transportation (DOT) statistics, weather accounts for more than 40 percent of all flight delays. A recent study commissioned by the Federal Aviation Administration (FAA) calculated that delays and cancellations from all causes cost passengers $16.7 billion a year. That puts the price tag on weather-related schedule disruptions at around $6.7 billion.

Your odds of avoiding a cancelled flight have a lot to do with the season. Summer thunderstorms can cause significant flight delays, but winter storms that blanket an airport with snow and ice may result in a higher rate of scratched flights. The all-time record for weather-related cancellations came in February 2010, according to the DOT's Bureau of Transportation Statistics. Some 4.2 percent of all scheduled U.S. flights that month didn't operate, thanks to a series of snowstorms. The worst day was February 10, when 23 percent of the nation's scheduled flights never took off. Historically, weather-related cancellations are highest in December, followed by January and February. The lowest weather-caused cancellation rates come in April through July.

Who decides if your flight will be delayed, diverted or canceled? That's a big question with no simple answer. Lots of eyes watch the weather: Airlines have dedicated staffs of meteorologists (usually outsourced), and the FAA works with a network of National Weather Service stations. When bad weather moves into an airport, the decision to reduce or stop flights is a collaborative effort. "It's done on a multitude of levels," says Ellen King, director of system operations for the FAA's Air Traffic Organization. "The local level is important, because they know exactly what's going on at the airport—but the final decision is not made at the local level."

That final call comes from the FAA's Air Traffic Control System Command Center in Herndon, Va., where the walls are lined with large monitors tracking the thousands of flights in the sky. FAA staff at this office stay in frequent teleconference contact with their counterparts at regional and local centers and at the airlines, and if the FAA determines—in some cases, after consulting local airport officials (if there's an issue of runway snow removal, for example)—that traffic at a specific airport needs to be cut back due to weather constraints, then a process called Ration by Schedule kicks in.

"If we have to reduce delivery to the airport [i.e., flight activity] by 40 percent, we'll go airline by airline and reduce their [schedule] requests by 40 percent, and that includes corporate and general aviation," King explains. So the FAA decides how many flights must be cut, but the individual airlines decide which ones.

Airlines start preparing for the possibility of cancellation as early as four to five days out, according to captain Jeff Osborne, managing director of American Airlines' System Operations Control Center in Fort Worth, Tex., where flight dispatchers are in constant contact with all AA aircraft worldwide. "We don't make decisions that far out—we're just thinking things through" based on advanced forecasts, Osborne says. As a weather event draws closer to a hub like Dallas–Forth Worth, American starts alerting nearby airports to get ready to accept diverted flights. If it's obvious that a major storm will hit the next day, Osborne says, American and other airlines will start preemptive flight cancellations; if the storm arrives suddenly, flights won't be scratched until the day of the event.

How do carriers decide which flights get the ax? "We have an automation tool that looks at all the complexities you can imagine that are behind the scenes," Osborne describes: "where the crews are going, airplane routings, what markets we want to protect. We tend to skew in favor of [operating] our wide-body flights that go international." American spokesman Tim Smith adds that the rescheduling tool "looks for high-frequency markets where we have a lot of capacity, and flights with fewer customers on board so we have fewer to reaccommodate."

If an airport requires weather-related flight constraints, the FAA might order a "ground stop"—halting departures to that destination from other airports—but those are always short-term, says King, and designed to prevent too many planes from clogging up the constrained airspace. Those flights already inbound to the affected airport are put into holding patterns. King says that flight diversions, where an inbound aircraft lands at an alternate airport, are not FAA commands but airline decisions usually made if the plane is short on fuel.

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