CHICAGO (AP) -- The Federal Aviation Administration has endorsed the city's $15 billion effort to expand O'Hare International Airport and reduce the nation's worst flight delays, but the plan still faces opposition from communities that would be gutted to build new runways and taxiways.
Mayor Richard Daley said construction would begin immediately after the FAA gives final approval for the plan, which is expected by September. The agency endorsed the plan Thursday in its environmental impact statement.
''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.
But a 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.
''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.
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.
Congestion at delay-prone O'Hare can quickly cause gridlock throughout the U.S. commercial aviation system. A Transportation Department study released earlier this year ranked O'Hare last in on-time departures and arrivals during 2004, with 30 percent of flights arriving late and 73 percent departing on time.
The plan's opponents claim the city has exaggerated the benefits of expanding the airport and lowballed the cost.
A report released last week by the U.S. Department of Transportation's inspector general also said the city has underestimated the project's cost, which could affect funding for airports nationwide because cities compete for money from the same federal program.
In addition, the report said the city has applied for an ''unprecedented'' $528 million in grants for the project, along with an additional $248 million for capital improvements over the next 20 years.
Daley on Thursday insisted that the city will have the funds to complete the expansion. Federal money would cover about 10 percent of the total cost, while revenue bonds and passenger facility charges would make up the rest, he said.
A cost-benefit analysis the city submitted to the FAA earlier this year projected the expansion would save more than $12 billion over nearly two decades by reducing passenger and aircraft delays _ a finding opponents deny.
The eight-year plan would reconfigure O'Hare's intersecting runway layout to a design of six parallel and two diagonal runways, which planners say would make it easier for planes to take off and land. The plan also includes a new terminal building, parking spaces for oversize planes and jet bridges.
The first new runway would open in 2007 and construction would be complete in 2013. The FAA report determined the project would result in only minimal impacts on air and water quality and noise levels.
To solve the gridlock problem at O'Hare, some politicians have proposed a third airport in the Chicago area. In April, Gov. Rod Blagojevich gave federal aviation officials a blueprint for a single-runway, five-gate airport near the town of Peotone. The airport would eventually expand to four runways and 12 gates and would be tailor-made for discount carriers.
Many aviation experts, however, are skeptical a third airport would draw the interest of airlines or passengers.