Chicago ? Federal officials announced an agreement Wednesday to temporarily ease congestion at O’Hare International Airport, a bottleneck that has created a cascade of flight delays throughout the nation.

The reduction of flight traffic is expected to reduce delays at O’Hare by about 20 percent and across the rest of the national air network by 5 percent, officials said.

“O’Hare will no longer be the place where on-time schedules come to die,” said Federal Aviation Administration Administrator Marion C. Blakey, who signed the agreement in Chicago along with Transportation Secretary Norman Y. Mineta.

The order, to take effect Nov. 1 and last through the end of April, cuts 37 daily peak-hour arrivals by United Airlines and American Airlines, the airport’s two largest carriers.

Mineta said the agreement would provide “breathing space” for the airlines, travelers and air-traffic controllers but was only a temporary solution to O’Hare’s congestion problems. Only about two-thirds of arrivals at O’Hare have been on time this year, compared with 80 percent systemwide.

The agreement followed negotiations earlier this month in Washington involving 16 airlines and the FAA. Mineta had called that meeting the last opportunity for airlines to voluntarily solve O’Hare’s gridlock before the government stepped in to impose strict flight caps.

United said Wednesday that it would accommodate the reduction by shifting most of its affected flights to off-peak hours, and an American spokesman said he did not expect the reductions to force a fare increase.

FAA official Sharon Pinkerton said the long-term solution to the flight congestion problem would be to add more capacity at O’Hare.