Air traffic controllers have been under strain for years, but a 90-second equipment failure last week exposed how decades of staffing shortages, underinvestment and patchwork solutions for those who guide planes through some of the world’s most congested airspace are taking their toll.

Caught in the middle of the issues at Newark is United Airlines, which is the most active airline at the New Jersey airport. While the problems lie with the FAA system, the airline is where people often aim their frustrations over cancellations and delays.

Workers at Newark Liberty airport lost communication with planes, now on 45-day leave 'to recover from the stress,' says FAA - Anadolu Ajansı

A communications outage at the Philadelphia Terminal Radar Approach Control affected air traffic at Newark Liberty. This highlights aging infrastructure and comes after Transportation Secretary Sean Duffy's proposal for major upgrades.

For years, the shortage of certified air traffic controllers in the US has led to flight ... delayed an average of almost four hours Sunday evening, according to an advisory from the FAA.

Several issues have led to delays and cancellations for about a week, and those disruptions were happening again Monday morning.