For years, the shortage of certified air traffic controllers in the US has led to flight disruptions and headaches for travelers across the country, most recently at busy Newark Liberty International Airport in New Jersey,

Hundreds of flights were canceled or delayed at Newark Liberty International Airport over the weekend and again on Monday as shortages of air traffic controllers persists, causing flight disruptions at one of the nation’s busiest airports.

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