A nationwide ground stop that halted U.S. flight departures for more than four hours on Friday stemmed from updates to a communication system managed by L3Harris Technologies, Transportation Secretary Sean Duffy said Saturday.
A router in a remote location overloaded other parts of the system, causing air traffic control centers to receive inconsistent information. The Federal Aviation Administration decided to ground flights because of instability in information feeds, FAA head Bryan Bedford said. No facilities went dark.
The FAA imposed the ground stop around 4 p.m. on Friday. It was the second nationwide ground stop since September 11, 2001.
Flight disruptions continued into Saturday. More than 3,700 U.S. flights were canceled Saturday and close to 2,000 were delayed as of 9:40 a.m. ET, according to FlightAware. Friday saw about 9,000 U.S. flight cancellations and more than 7,000 delays, though some disruptions were due to bad weather.
Around 3 million people were scheduled to fly on Saturday, according to Cirium.
Bedford said there was "zero evidence" the problem was caused by something "nefarious" or related to artificial intelligence. Trump administration officials said it did not appear to be a cyberattack.
American Airlines is offering flight attendants extra pay to pick up trips. Delta Air Lines gave flight crews confirmed seats on flights to reposition them. Both American and other airlines said they would change customers' tickets at no fee or fare difference if the outage affected their plans.
Duffy blamed outdated U.S. infrastructure for the problem and said Congress needs to approve more money to overhaul air traffic control systems.