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CHICAGO (Reuters) - Chicago would spend $8.5 billion over eight years to expand its O’Hare International Airport under a plan Mayor Rahm Emanuel is expected to introduce to the city council on Wednesday, the Chicago Tribune reported on Monday.

The plan, which involves a new use and lease agreement with airlines, would be financed with airport bonds.

Molly Poppe, a spokeswoman for Chicago’s finance department, said the city would use “traditional airport financing mechanisms,” adding that details would be released soon.

Most of the money would be earmarked for replacing one of the existing terminals with a new global terminal, where the airport’s largest carriers, United Airlines [UALCO.UL] and American Airlines Group Inc, would be relocated, the Tribune said.

The two airlines declined to comment on the plan, citing ongoing negotiations with the city.

“We look forward to continuing to work collaboratively in order to finalize an agreement that will mean continued investment at O’Hare and a world-class airport for the traveling public and people of Chicago,” Charles Hobart, a United spokesman, said in an email.

Chicago has already spent billions of dollars to reconfigure and extend runways at the airport.

O’Hare is the world’s second-busiest airport in terms of take-offs and landings after Atlanta’s Hartsfield–Jackson International Airport, according to an Airports Council International 2016 ranking.