The former head of the US National Transportation Safety Board says there hasn't been such a widespread shutdown of US flights since the September 11, 2001, attacks.
Robert L. Smollett told CBS News, the BBC's US media partner, "It's really amazing that it's happening these days. ".
He noted that in 2023 there was also a short break in flights, which lasted only a few hours.
Smollett says it's unclear exactly what went wrong, but added that there are 22 air traffic control centers in the U.S. located at high altitudes that monitor planes when they fly above 10,000 to 10,000 feet.
"It seems that there were disruptions in these facilities. The FAA realized there was a problem, so it took the right action to ensure no planes were allowed to take off until the problem was resolved. ".
The Federal Aviation Administration said the flight suspensions were due to "urgent" reasons.
"Obviously, when the ability to communicate with air traffic control is reduced, there is an immediate problem," Mr Smollett said. "So, I think it's the right thing to do, because they're not allowing more air traffic into a system that's already under a lot of pressure in the current situation. ".