Despite efforts by U.S. Rep. Jesse Jackson Jr. (D-Ill.) to garner support for construction of a new airport in south suburban Chicago, Chicago Mayor Rahm Emanuel has indicated construction of a fourth runway at Chicago's O'Hare Airport would eliminate need for a third regional airport.

“I understand what he has to do as a congressman, but as a mayor, I have my interests representing the city and that means expanding O'Hare and its capacity, because if it runs on rails, if it runs on roads and if it runs on runways, it's coming through Chicago,” Emanuel said Tuesday, while attending ground breaking for a two-mile extension of Chicago's Lake Shore Drive (US-41).

The event marked the second time in a week Emanuel discussed plans to proceed with a fourth runway at O'Hare, part of a planned expansion originally proposed by former Chicago mayor Richard M. Daley. The multi-billion-dollar proposal ultimately calls for constructing four new runways and extending a pair of existing ones in order to reduce delays and increase capacity at O'Hare.

A fourth runway would “reduce delays by 80% and raise the airport's capacity by 300,000 passengers per year by 2015,” Emanuel said at a March 29 press conference. “To help us accomplish this goal, I call on the airlines to begin planning with us today.”

American and United Airlines, 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.

To date, neither airline has indicated strong support for a fourth runway. American, under court supervision since filing for Chapter 11 bankruptcy in November, “is very supportive of modernizing O'Hare,” according to a statement. “However, we remain completely focused on our restructuring and have limited ability to make commitments going forward.”

United Spokeswoman Megan McCarthy told reporters the airline “would continue to work with the city on demand-driven projects.”

In 2011, United and American Airlines agreed to support a third runway after suing the city for securing loans for an expansion without their consent.