In a letter to customers sent Friday, United CEO Scott Kirby said the Federal Aviation Administration’s longstanding staffing problems finally "boiled over" this week, as technological problems caused dozens of diverted flights, and hundreds of canceled and delayed ones. Kirby said 20% of the air traffic controllers walked off the job as well.

United is Newark Airport‘s largest carrier. Cutting 35 flights means slashing about 10% of its daily agenda at the airport, where the airline flies an average of 328 flights a day. A spokesperson for the Port Authority of New York and New Jersey, which manages New Jersey’s airports, did not immediately respond to a request for comment.