Since November, airlines at O'Hare - the nation's busiest airport based on total flights - have voluntarily reduced flights to 88 an hour between 7 a.m. and 8 p.m., down from a maximum of more than 130 an hour. That agreement, which was to expire April 30, has already been extended through October.
On Tuesday, the FAA proposed a federal rule that would extend the flight limits until April 2008, when O'Hare might be able to handle more flights, the FAA said.
''While we are working hard to add capacity throughout the system, we need to make sure in the interim that O'Hare schedules don't exceed what the airport can handle,'' FAA Administrator Marion Blakey said in a statement.
The FAA is expected to decide in September whether to approve a proposed $15 billion (euro11.39 billion) expansion of O'Hare that would add two new runways and reconfigure others. If the plan is approved, a new runway could be finished by late 2007, allowing more flight arrivals, FAA spokesman Tony Molinaro said.
If the FAA rejects O'Hare's expansion plan, a three-year reduction in flights would give the agency more than two years to figure out other ways to add capacity at the congestion-prone airport, Molinaro said.
Since the voluntary flight reductions took effect, on-time arrivals at O'Hare have improved by 17 percent and overall delay minutes have been cut 22 percent, the FAA said.
The FAA said keeping the flight limits in place three more years would cut delays at O'Hare 42 percent. The agency would review delay information every six months to see if the airport could handle more flights.
Representatives of the airport's two busiest carriers - UAL Corp.'s United Airlines and AMR Corp.'s American Airlines - objected Tuesday to part of the rule that would give new or small carriers the first chance to add flights if O'Hare's capacity increases over the three years.
''We have stepped up to help out, so we feel we should be the first to be made whole when there is new capacity available,'' United spokesman Jeff Green said.
American Airlines spokeswoman Mary Frances Fagan said the carrier has voluntarily reduced its flights into O'Hare by more than 13 percent since November. She said American and United should be the first to take advantage of extra capacity.
Airlines and others will have the opportunity to comment on the proposed rule to extend the flight reductions before the FAA makes a decision, Molinaro said.