But in the meantime, critics still have questions.
"Do you really have to tear up a lot of runways or do as grandiose a plan as is in play? I'm not sure you do," said Aaron Gellman, a professor at Northwestern University's Transportation Center.
Gellman says improvements to the region's air traffic control system, for example, could go a long way toward increasing O'Hare's capacity.
The project's well-organized, well-financed foes also argue the project will drive up prices for travelers and will not reduce delays because increased capacity will be absorbed with more flights.
"Be prepared for delays the likes of which you've never seen before, and be prepared to pay a whole lot more for your airline ticket," says Joe Karaganis, an attorney for the suburbs and cemetery.
On the Net:
O'Hare Airport: http://www.ohare.com/
City advances plan to expand airfield despite opposition.
The center will monitor 1 of 2 new runways at O'Hare Airport.
Chicago has promised that its $14.7 billion plan virtually will eliminate late and canceled flights during bad weather.
Chicago aviation officials like to point to the 31-year-old airport in Dallas as a proven model for the parallel runways envisioned at the future O'Hare International Airport.