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.

A deadly midair collision in January between a military helicopter and a commercial airliner, and several crashes since, have prompted officials to focus on fixing the nation’s outdated air traffic control system and hiring more controllers.