US flight disruptions could last days

US flights were slowly resuming departures and a ground stop was lifted after the Federal Aviation Administration (FAA) scrambled to fix a system outage overnight that had forced a halt to all US departing flights.
More than 7,300 flights were delayed and 1,100 canceled according to the FlightAware website in the first national grounding of flights in about two decades, industry officials said.
The total was still rising and officials said the outage could cause delays through at least Thursday, if not longer, according to several airlines.
The cause of the problem with a pilot-alerting system was unclear, but US officials said they had so far found no evidence of a cyberattack. US Transportation Secretary Pete Buttigieg told CNN an issue with overnight "irregularities" with safety messages sent to pilots prompted the outage.
The outage could impact traffic through Friday, said Captain Chris Torres, vice president of the Allied Pilots Association.
One issue airlines are facing is trying to get planes in and out of crowded gates, which is causing further delays. Crew time limit rules may also play a factor.
The FAA had earlier ordered airlines to pause all domestic departures after its pilot alerting system crashed and the agency had to perform a hard reset around 2 am, officials said. Flights already in the air were allowed to continue to their destinations.