Three weeks ago, Chicago Mayor Rahm Emanuel called on American and United Airlines to support construction of a fourth runway at O'Hare International Airport in order to raise capacity and reduce delays at the Midwest's largest hub.

Thursday, United Continental Holdings CEO Jeff Smisek responded, but not with an answer Emanuel wanted to hear.

When asked during a public appearance what type of additional expansion O'Hare would require to meet current or future demand, Smisek replied, “None. The project that we have now is more than sufficient for any reasonably foreseeable demand.”

American and United, O'Hare's two largest carriers, must approve capital projects funded by bonds, since repayment relies on the landing fees and other charges they generate. In 2011, the two airlines agreed to support a third runway after suing the city for securing loans for a multi-billion-dollar  expansion without their consent.

Smisek indicated that construction of a new airport in south suburban Chicago, a proposal supported by U.S. Rep. Jesse Jackson Jr. (D-Ill.), also isn't warranted. “There's no demand for it,” he said. Any benefits, he added, would be “vastly overshadowed...by the damage it would do to O'Hare.”

Rather than increase capacity in the region, Smisek indicated O'Hare should modernize its air traffic control systems. He elaborated that implementing satellite-based systems rather ground-based radar would increase productivity while resulting in less jet fuel use and fewer emissions.”

American, under court supervision since filing for Chaper 11 bankruptcy in November, indicated in March it is “very supportive of modernizing O'Hare. However, we remain focused on our restructuring and have limited ability to make commitments going forward.”