US airlines expect to restore full flight schedules by Sunday night after Friday’s nationwide ground stop, with Federal Aviation Administration (FAA) chief Bryan Bedford projecting 4,000 to 5,000 cancellations on Saturday, NBC News reported.

The FAA halted departures nationwide for more than four hours on Friday after an equipment outage disrupted radar feeds and communications with aircraft. It lifted the ground stop at 8:15 pm ET, NBC said.

Bedford said the air traffic control system was stable on Saturday morning but that airlines still faced significant recovery work, according to the report.

Officials said they found no evidence of a cyberattack or of any role for artificial intelligence in the outage, NBC reported. Transportation Secretary Sean Duffy said the affected systems came back online after officials isolated the problem at a remote FAA site. Investigators are still examining whether the outage stemmed from faulty equipment, installation, or configuration.

NBC said Duffy had blamed the aerospace contractor L3Harris for the ground stop. L3Harris said it is cooperating with the FAA’s investigation.

American Airlines said on Saturday night that all cancellations resulting from the ground stop had been completed, though some individual flights might still be cancelled as it restores its schedule. “All planned cancellations for tonight and tomorrow have now been completed,” the airline said in a statement. It said it was planning a “strong start” on Sunday.

Heather Garboden, American’s chief customer officer, said in a message to customers that they should still expect disruption through the end of Sunday. “A ground stop of this magnitude is especially disruptive because its effects compound quickly,” she said. She called the event among the most significant operational impacts the airline has experienced and apologised for the inconvenience.