About 300 flights per day must be cut from the schedule at Chicago O’Hare International Airport on the busiest days this summer in an effort to reduce flight delays, federal officials announced Thursday.

“If you book a ticket, we want you and your family to have the certainty that you’ll fly without endless delays and cancellations,” Transportation Secretary Sean Duffy said in a statement.

O’Hare has the most number of flights of any US airport, and it already had one of the worst records for flight delays nationwide last year.

More than 3,080 flights were planned on peak days this summer, which represented a 14.9% increase from the summer before, according to the US Department of Transportation and Federal Aviation Administration.

That increase comes as air traffic controllers deal with taxiway closures for construction projects.

In its draft order, the federal government said both American and United announced expansion plans at O’Hare that could lead to significant delays this summer and limit the airfield’s ability to handle the expected amount of traffic.

Duffy said that the schedule was unrealistic and would have exceeded what the airport could handle.

So the number of flights at the airport will be limited to a maximum of 2,708, which is still slightly higher than maximum of 2,680 flights that were scheduled at the peak of last summer.

He said that “will reduce delays and make this busy summer travel season a little easier.”

On slower days of the week, fewer flights will have to be cut because a smaller number was scheduled in the first place. Tuesdays, Wednesdays and Saturdays are typically slower days of the week for flights.

The flight limits will take effect May 17 and last through Oct. 24.

Airlines will go through the details of the order to figure out how many flights they have to cancel and then will notify customers.

American Airlines said that once implemented, the FAA’s order will improve reliability and reduce delays for customers traveling through O’Hare this summer.

“We are grateful to Secretary Duffy, Administrator Bedford, and their leadership teams for acting swiftly to ensure that Chicagoans and all consumers continue to benefit from sensible competition and to help minimize flight disruptions during the busy summer season,” American said in a statement.

American told employees in a memo that it estimates that it will have to cut no more than 40 arrivals and departures per day, but it estimates that United might have to cut more than 200 arrivals and departures based on the published schedules.

United did not provide an estimate of how many flights it will have to cut.

United said the airline appreciates that the government came up with “a solution that makes sense for everyone who cares about O’Hare’s success.”

Both airlines will review the order and their scheduled to determine where to make cuts and then notify travelers who are affected.