CHICAGO (CBS/WBBM) — Two major airlines are threatening to sue over the next proposed phase of the expansion of O’Hare International Airport.

As WBBM Newsradio 780’s Regine Schlesinger reports, United and American airlines have been on a collision course with the city over plans to issue bonds to finance the next phase of the O’Hare Modernization Program, which will cost more than $3 million.

LISTEN: Newsradio 780’s Regine Schlesinger reports

Crain’s Chicago Business reports the two airlines might sue over what they characterize as a violation of the contract that gives them veto power over major projects that increase their operating costs at O’Hare.

The city contends that the provision does not apply to bonds payable after May 2018, when the contract expires.

The airlines have been arguing recently that with traffic decreasing and fewer delays, O’Hare expansion should be scaled back.

Late last year, the City Council approved a plan to issue $1 billion in bonds for the O’Hare expansion project. Last week, reports surfaced that the bonds Moody’s had been downgraded some of the bonds, on the grounds that the city has been unable to get financial support from the airlines.

The O’Hare Modernization Program calls for building one new runway, extending another runway and relocating a third. A new northern runway opened in November 2008, and about 500 former homes and businesses in west suburban Bensenville are being demolished to make way for the expanded airport.

St. Johannes Cemetery is also being moved for the project.

But overall, the $15 billion expansion project is still less than halfway done.

Watch & Listen LIVE