Newark Airport passengers on Wednesday got a brief respite from the ongoing flight delays and cancellations that have been plaguing the airport in recent days. However, that break appears to be over.

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.

The agency plans a multibillion-dollar upgrade effort, including new fiber-optic data lines between New York and Philly.