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.

United has been urging the government to limit the number of flights to what an airport can realistically manage based on staffing, CEO Scott Kirby said.