Air traffic control staffing issues are cascading into major delays for passengers flying in and out of the busy Newark airport outside of New York City for an unprecedented fifth day in a row.

More delays at Newark Liberty International Airport are being reported Friday, continuing a wave of late flights that has been plaguing travelers all week. Many flights out of Newark have been delayed for at least one hour Friday,

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.