The CEO of United Airlines penned a letter to employees outlining what he thinks the Federal Aviation Administration needs to do to fix all the delays plaguing Newark Liberty International Airport. The delays began last Monday when crews in the Philadelphia air traffic control facility that lines up flights into and out of Newark lost radar and communications with the planes for at least 30 seconds.

United Airlines CEO Scott Kirby told CNN Thursday air travel remains safe, even at Newark Liberty International Airport, where delays have played out for more than a week as air traffic controllers took trauma leave after a critical technology outage.

Passengers with flights to or from Newark Liberty International Airport are encountering long delays and cancellations due to an air traffic controller shortage and equipment failures.