Air traffic resumes at LaGuardia after FAA outage

STORY: The cause of the problem, which delayed thousands of flights in the United States, was unclear, but U.S. officials said they had so far found no evidence of a cyberattack.

"Normal air traffic operations are resuming gradually across the U.S. following an overnight outage to the Notice to Air Missions system that provides safety info to flight crews. The ground stop has been lifted. We continue to look into the cause of the initial problem" the FAA said in a Tweet.

More than 4,300 flights had been delayed and 700 canceled as officials said it will take hours to recover from the halt to flights.