Planes are seen on the tarmac as people wait for their flight reschedule inside of the Newark International Airport on June 27, 2023 in Newark, New Jersey. Kena Betancur | Getty Images News | Getty ImagesUnited Airlines’ CEO Scott Kirby said that without more gates the airline will have to reduce or change schedules to handle frequent gridlock at its Newark, New Jersey, hub, a message that came after mass flight delays marred July Fourth holiday weekend travel. The carrier gave 30,000 frequent flyer miles to customers who were most affected by the chaos.”This has been one of the most operationally challenging weeks I’ve experienced in my entire career,” Kirby said in a note to staff, which was seen by CNBC on Saturday.He said that the airline needs more gates at Newark Liberty International Airport because of frequent aircraft backups there. “We are going to have to further change/reduce our schedule to give ourselves even more spare gates and buffer — especially during thunderstorm season,” he added.A day earlier, Kirby apologized for taking a private jet out of New Jersey’s Teterboro Airport while thousands of passengers were stranded, CNBC first reported Friday.Problems began with a series of thunderstorms in some of the country’s most congested airspace along the East Coast last weekend, cutting off routes for aircraft. While most airlines recovered, United’s problems continued during the week, angering both customers and crews. United and JetBlue Airways executives said air traffic control problems worsened the disruptions.Kirby laid out the weeklong troubles and said long-term changes were needed. He said that extensively delayed departures, which piled up at its hub at Newark since last weekend, hurt its operation. Takeoffs were delayed by as much as 75% for longer than 8 hours in some cases from Sunday through Tuesday.”Airlines, including United, simply aren’t designed to have their largest hub have its capacity severely limited for four straight days and still operate successfully,” he wrote.Aircraft and crews were then left out of position, something that happens often during severe weather and can spark a cascade of disruptions for customers.Unions complained about hours-long waits for crew members to get assignments and get hotels, forcing them to stay at airports longer.Kirby said the carrier must improve the platforms so crews can get assignments and accommodation more easily on its app, saying what happened over the past week isn’t acceptable.Kirby called for more investment in the FAA and air traffic control to avoid delays and staffing shortages, some of which occurred after hiring and training paused early in the pandemic.United sent the 30,000 miles to customers who were delayed overnight or didn’t get to their destination at all, a spokeswoman said. She declined to say how many customers received the email.More than 42,000 U.S. flights arrived late from last Saturday through Friday and more than 7,900 were canceled — or more than 5% of airlines’ schedules — a rate that was more than triple the average so far this year, according to flight-tracker FlightAware. United fared worse than competitors with about half of its mainline schedule arriving late and almost a fifth canceled over that period, FlightAware data show.United’s operation improved on Saturday but disruptions lingered. About 11% of its mainline schedule, or close to 300 flights were delayed and 43 flights, or 1% were canceled, down sharply from 1,324 delays and 252 cancellations on Friday.