Operations have returned to normal after another air traffic control equipment outage caused the Federal Aviation Administration to implement a ground stop for Newark Liberty International Airport-bound flights Sunday morning.

The air traffic control mishap early Friday morning added to disruptions in recent days that have intensified concerns about safety at one of the busiest U.S. airports.

The mounting air traffic control problems at Newark Liberty International Airport caused aviation officials to implement a ground stop for flights on Sunday morning, the third such incident in the past two weeks.