The Federal Aviation Administration on Thursday endorsed Chicago's $15 billion plan to expand O'Hare Airport to relieve congestion and reduce the worst flight delays in the nation.
Mayor Richard Daley said construction would begin immediately upon receiving final approval, which is expected next month.
"When we reduce delays at O'Hare, it will speed up air travel throughout the nation, saving millions of dollars in time and fuel," Daley said.
The plan calls for building new runways and taxiways and reconfiguring others. The first new runway would open in 2007 and construction would be complete in 2013.
The project could still face legal challenges from opponents who claim the city has exaggerated the benefits and lowballed the cost.
"You cannot approve a project that can't be paid for and would cause more delays than it solves," said Joe Karaganis, an attorney for Elk Grove Village and Bensenville, suburbs that have fiercely fought O'Hare expansion for decades.
The 440-acre expansion would require the city to buy and raze more than 500 homes, displacing some 2,600 residents, and would require relocation of nearly 200 businesses and a cemetery with 1,300 tombs dating back to the 1800s.
Jared Leland, an attorney for the owners of the threatened cemetery, said his clients would sue if the FAA decides in favor of the plan.
A report released last week by the U.S. Department of Transportation's inspector general said the city has underestimated the project's cost. It said the city has applied for an "unprecedented" $528 million in grants for the project.
But Daley on Thursday insisted that the city will have the funds to complete the expansion.
The U.S. Transportation Department ranked O'Hare last in on-time departures and arrivals in 2004. Thirty percent of flights arrived late that year.