Whenever there’s an issue in the nation’s airspace, like the current string of delays and cancellations at Newark Liberty International Airport, air traffic controllers come under a microscope.

The Federal Aviation Administration has about 14,000 air traffic controllers. More than 1,800 were hired last year, the largest number in nearly a decade, and the government is on track to hire even more this year. Still, there’s a need for about 3,000 more to fully staff the system.

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.