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and a commercial airliner, and several crashes since, have prompted officials to focus on fixing the nation’s outdated air traffic control system and hiring more controllers.

The air traffic system meltdown at Newark Liberty International Airport last week “was the most dangerous situation you could have,” according to an air traffic controller on duty that day, as the fallout from the outage stretches into a second week.

Audio between air traffic controllers and pilots at Newark Airport reveals the moment the tower lost radio contact with planes.