A new runway is allowing airplanes coming into O'Hare International Airport to shave several precious minutes off their time in the air but is also forcing those jets to spend more minutes taxiing to their gates after they have landed.
The new east-west runway that is part of an ongoing O'Hare expansion opened in October, and the airlines and air traffic controllers are just now discovering its impact.
So far, the time savings in the air appears to be washed out as planes line up on congested taxiways and travel greater distances to terminals to avoid crossing active runways, according to air traffic data and interviews with airline officials, pilots and controllers.
And with winter still ramping up, O'Hare faces its first major test involving strong crosswinds blowing over the new east-west parallel runway configuration. High crosswinds threaten to reduce flight operations or ground planes entirely until gusts subside, leading to delays and cancellations.
"We, along with other airlines, the Chicago Department of Aviation and the (Federal Aviation Administration) are still learning the best way to utilize the new runways in the most efficient way," said Christen David, a United Airlines spokeswoman.
Today taxi times to the gate are generally longer than they were several months ago because of a longer route that takes arrivals an extra mile or more around the airfield. The purpose is to have the planes taxi behind other planes waiting to take off so as to reduce the possibility of collisions, airline and FAA air traffic officials said. The taxiing time and distance vary, based on the runway and the gate involved.
Any time saved in the air can be canceled out by the additional time spent on the ground.
"It is a longer taxi route, designed to keep you from taxiing across active runways," said Halli Mulei, a Chicago-based first officer who has flown for United Airlines for 17 years. "But we are flying a shorter final (approach) into O'Hare, saving fuel and about 10 minutes."
The new parallel runway alignment has increased flight capacity at O'Hare, especially important in less-than-perfect weather conditions.
From the Oct. 17 opening through Dec. 11, O'Hare has been able to accommodate 112 or more landings per hour on average on 68 percent of the days, according to the FAA.
That compares to a rate of 112 or more arrivals per hour only 20 percent of days in November 2012, FAA data show.
"We will not draw any conclusions yet from this data (because) the sample size is too small," FAA spokesman Tony Molinaro said.
Despite the big capacity gains, on-time performance at O'Hare — the measurement that matters most to air travelers and a selling point of the runway project — hasn't changed as dramatically.
Eighty-two percent of O'Hare arrivals parked at the gate on time in October, according to the U.S. Department of Transportation's Bureau of Transportation Statistics. That's down slightly from 84 percent on-time arrivals in September, but up compared to October 2012, when 75 percent of O'Hare arrivals parked at the gate on schedule. Data for November are not yet available.
It's still very early in what amounts to an unprecedented transformation of O'Hare's runway alignment, eventually culminating in six parallel east-west runways, two runways running northeast to southwest and the elimination of two other diagonals that run northwest to southeast.
O'Hare currently uses four east-west parallel runways, with a fifth set to open in 2015 on the south airfield. The city of Chicago and the airlines have not reached an agreement on building a planned sixth parallel runway.
At this stage in the completion of the new configuration, air traffic uses the east-west runways about 95 percent of the time, according to the FAA. Since the new runway opened in October, the vast majority of landings and takeoffs move from west to east, the FAA said. The airport's four diagonal runways are used sparingly, mainly when strong crosswinds — from the north or from the south — exceed the performance limitations of most aircraft to use the east-west runways.
With the predominant jet stream in the U.S. coming from the west, the new runway alignment and westerly flow pattern are designed to allow planes to take off and land into the wind most of the time. It's an ideal condition for achieving the airspeed needed for takeoff using the least amount of runway and for avoiding a tail wind during landing, which would require a longer braking distance on the runway.
The combination of runways in use will no longer change every time the wind does, saving time, airline and air traffic controllers say. It can be frustrating to pilots and passengers alike when a plane, No. 1 in line for takeoff, suddenly becomes No. 17 because the winds shifted and the runway they were on shuts down.
But some pilots and controllers are concerned that with the strong reliance on the east-west runways, O'Hare will lose some of its flexibility to cope with the Chicago area's wind patterns.