Ever noticed how a flight from Atlanta to New York takes longer than it used to?
The not-so-hidden secret is that airlines have been adding minutes to flight times to improve their on-time performance, as well as to prevent everything from mishandled baggage to missed connections.
Airlines know that their on-time rates are closely monitored by the federal government. What's more, delays that may disrupt passengers' trips can increase complaint rates and affect their willingness to fly the airline again. Delays might also keep passengers from catching connecting flights, which wreaks havoc on travelers' schedules and airline operations.
Atlanta-based Delta Air Lines, for example, has been adding extra minutes onto the airline's estimated “block times” -- the periods that begin when blocks are removed from a plane's wheels at the gate of departure and end when the blocks are placed around the wheels at the destination -- to allow for congestion. The result adds to the amount of time passengers have to allocate for travel generally, on top of security waits.
"It's an unfortunate byproduct of traveling," said George Nathan, who lives in Atlanta and flies for business once every two weeks or more. "You can't trust airlines to be on time. ... You learn over time which departure or arrival schedules you can trust and which ones you can't."
Contributing to longer estimated block times are a number of variables, from air traffic control congestion to airline over-scheduling during peak periods to long taxi times, according to Delta.
Nathan is skeptical about airlines' motivations.
"They may look better statistically, but none of this is done for what I call passenger comfort or passenger care," Nathan said.
But Dave Holtz, Delta's managing director of operations, doesn't think of it as "padding" the schedule.
"You're just predicting around what reality is in the aviation world, not necessarily padding to make a number or trying to fool a customer," he said.
In 2002, airlines posted an on-time arrival performance of 82.1 percent. Last year, airlines' on-time performance was 79.8 percent.
Getting the estimate right is difficult and varies depending on the time of day and time of year, due to fluctuating air traffic and other factors, Holtz said.
About two-thirds of extra block time covers air traffic control congestion, while about one-third is for taxi time, he said.
In Atlanta, about 15 to 20 minutes are allowed for taxi times, he said, while other airports may have as much as 30 minutes built in for taxiing. While Hartsfield-Jackson International is the busiest airport in the world,, the air traffic system is not as complex as that in New York, where several airports share the same airspace, he said.
"I like to use the example of your commute to work. I can drive to work in 40 minutes during peak hours ... yet I can make it in about 25 minutes during overnight hours," Holtz said.
Congestion at peak periods in New York is one of the big factors for heavy delays in Delta's route network.
"That always makes the prediction of our block times a little bit more difficult to manage," Holtz said.
A flight from Atlanta to LaGuardia is allotted roughly 2 hours and 15 minutes during slow periods, but goes up to as much as 2 hours and 45 minutes during rush hour at the airport -- 7-10 a.m. and 4-7 p.m. -- according to Holtz.
The problem has worsened over the years as congestion increases.
"There is no doubt that the Atlanta-LaGuardia flight time of 2 hours and 45 minutes during that peak period was less than that 10 or 15 years ago," Holtz said.
Block times also vary more on longer international flights, which are more affected by upper-level wind patterns. Arrival times can vary by as much as an hour between summer and winter, he said.
Itai Ater, a professor at Tel Aviv University who wrote a paper about how over-scheduling affects longer block times in hub airports, said airlines' practice of scheduling many flights at the busiest times contribute to delays of other airlines.
"This is particularly true in large, busy airports where several airlines operate," according to Ater.
Accurate scheduling is a key factor in a large hub operation, Holtz said. If the first flight is delayed, that can affect the second, third and fourth flights scheduled on that plane for that day.
"It's a domino falling, if you will," Holtz said. "The end result is it affects every metric."
And after a summer rife with delays in 2010, Delta has focused on improving its performance this year, coordinating pilots, flight attendants and ground crew to make sure the aircraft is ready to go. On-time performance is part of Delta employees' goals for financial incentives.
Still, allowing too much block time can be just as bad. Early-arriving planes may have to wait on the tarmac for a gate to become available, which upsets passengers.
"Coming into Atlanta early, we constantly face the problem of the pilot saying we've arrived early, but there's another plane at our gate and we're going to have to sit here a few minutes on the ramp," Nathan said. "It's very frustrating."
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