Explainer-Why U.S. flights were grounded by a FAA system outage

A view of flights parked at the Orlando International Airport, as flights were grounded after FAA system outage, in Orlando, Florida, U.S., January 11, 2023 in this picture obtained from social media. Lou Mongello/via REUTERS

(Reuters) - The Federal Aviation Administration (FAA) allowed some flights to resume after an outage of the system that alerts pilots to any obstructions before take-off had earlier forced the civil aviation regulator to ground all aircraft in the United States.

Over 4,000 flights were delayed and more than 600 canceled because of the outage as of early Wednesday morning. U.S. flights were slowly beginning to resume departures as a ground stop was lifted.