United Airlines CEO Scott Kirby is urging the Federal Aviation Administration to increase air traffic controller staffing at Chicago O'Hare International Airport, where aircraft taxi times rank among the longest in the United States.

According to FAA data cited by ABC7 Chicago, aircraft at O'Hare average 28 minutes taxiing from the gate to takeoff and 20 minutes traveling from the runway to the gate after landing.

Speaking at the Executives' Club of Chicago, Kirby attributed some of the delays to air traffic control staffing shortages and the airport's runway configuration, which requires aircraft to travel around runways rather than cross them.

Kirby said O'Hare's south control tower is frequently unstaffed, limiting runway utilization. When the tower is staffed, he said, aircraft taxi times can be reduced by six to seven minutes per flight.

The concerns come as O'Hare experiences growing flight activity and undergoes a major terminal expansion. Earlier this year, the FAA imposed limits on flight operations amid concerns about congestion and available infrastructure.

Kirby said additional air traffic controllers would help the airport make better use of its existing capacity and improve operational efficiency.

The FAA and Chicago Department of Aviation had not responded to requests for comment at the time of ABC7's report.