CHICAGO (AP) _ Gov. George Ryan outlined a $6 billion plan Thursday to expand O'Hare International Airport and build another airport south of Chicago.

The plan, begun long before the recent drop-off in air travel due to terrorist attacks, aims to reduce the delays that have frustrated O'Hare travelers for years.

``Since September the 11th, we've become much more aware that air transportation is a vital, crucial part of our nation's economy,'' Ryan said. ``That is especially true in the Chicagoland region, which is the center of air transportation in the United States.''

The proposal incorporates most of an O'Hare plan that Mayor Richard M. Daley announced in June. But it also tries to appease suburban residents by limiting flights at O'Hare and eliminating a new runway included in Daley's plan.

Daley said he'll work with Ryan on a final proposal, which will require federal approval.

In both plans, three runways would be rebuilt during the next 10 to 15 years. The runways would run parallel, rather than crisscross, making it easier to move planes in and out of the airport.

The governor also wants to build an airport in Peotone, about 40 miles south of Chicago. The major airlines have said they're not interested, and Ryan said he had not yet determined how to pay for it.

``If you build what the governor's proposed today, you cannot justify the south suburban airport at all,'' said Joe Karaganis, attorney for the Suburban O'Hare Commission, which opposes O'Hare expansion.

The Federal Aviation Administration in April ranked O'Hare third in the nation for delays, after LaGuardia Airport in New York and Newark International Airport in New Jersey.