United Airlines (UAL) Chief Executive Officer Scott Kirby said Wednesday in an update to employees that all the flights in and out of the Newark Liberty International Airport (EWR) are "absolutely safe."

Kirby said when there are issues including technology outages and staffing shortages, among others, the Federal Aviation Administration requires all airlines to slow down aircraft and/or cancel flights to maintain the highest levels of safety.

"Neither the FAA nor United pilots will ever compromise on safety," Kirby said, adding that the airline is determined to solve the issues that cause the delays or cancellations for the long-term.

Under ideal conditions, the airport can only handle 77 flights per hour as per the FAA. However, it "regularly approves schedules of 80+ flights per hour almost every day between 3:00pm and 8:00pm. This math doesn't work. Especially when there is weather, staffing issues or technology breakdowns - the airspace, taxiways, and runways get backed up and gridlock occurs," Kirby said in the update to employees.

Kirby said only the FAA can actually fix the airport. He suggested that the FAA should limit the airport to 48 flights per hour while the runway is under construction; return the airport to a level-3 slot controlled airport; modernize the air traffic control system and get the airport's ATC fully staffed.

The FAA said in a Wednesday note posted on its website that departure traffic is experiencing gate hold and taxi delays for 15 minutes or less, and arrival traffic is experiencing airborne delays of 15 minutes or less.

UAL shares were up 3.5% in recent trading.

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