City officials said the average delay per plane will shrink to six minutes, compared with 15 minutes on the existing airfield. Delays at the reconfigured O'Hare are based on computer simulations in which planes take off, land and taxi to gates in perfectly spaced intervals, while the delay figure for the existing airport reflects actual performance.
The cornerstone of the city's runway plan, which Daley first trumpeted in 2001, was to cut delays in bad weather by 95 percent and delays overall by 79 percent while still increasing the number of flights. When the Tribune asked the FAA to test this promise using its own computer models, the agency came up with delay reductions of 68 percent for bad weather and 66 percent overall. FAA officials said the city's calculation failed to factor in the increased flights.
The FAA projects that increased demand for air travel at O'Hare could reach 1.4 million annual flights, up from 974,000 today. That increased traffic would spark a return to the kinds of lengthy delays that the massive expansion is trying to fix just five years after the runways are complete, according to FAA documents.
"In the world of airport development, there is no denying that if demand increases, eventually you find yourself back where you started," said Barry Cooper, a top FAA official who is reviewing the city's expansion plan. "It's a matter of investing in how many years of better performance you are looking to get."
By Jon Hilkevitch and Patricia Callahan