ap photo A Southwest Airlines passenger jet takes off from Chicago’s Midway Airport as flight delays stemming from a computer outage at the Federal Aviation Administration brought departures to a standstill across the U.S earlier Wednesday, in Chicago.

NEW YORK — Thousands of flights across the U.S. were canceled or delayed Wednesday after a system that offers safety information to pilots failed, and the government launched an investigation into the breakdown, which grounded some planes for hours.

The Federal Aviation Administration said preliminary indications “traced the outage to a damaged database file.” The agency said it would take steps to avoid another similar disruption.

The breakdown showed how much American air travel depends on the computer system that generates alerts called NOTAMs — or Notice to Air Missions.

Before a plane takes off, pilots and airline dispatchers must review the notices, which include details about bad weather, runway closures or other temporary factors that could affect the flight. The system was once telephone-based but moved online years ago.

The system broke down late Tuesday and was not fixed until midmorning Wednesday. The FAA took the rare step of preventing any planes from taking off for a time, and the cascading chaos led to more than 1,300 flight cancellations and 9,000 delays by early evening on the East Coast, according to flight-tracking website FlightAware.

Transportation Secretary Pete Buttigieg told a news conference that the problems “led to a ground stop because of the way safety information was moving through the system.”

After the failures were fixed, he warned that travelers could continue to see some effects “rippling through the system.”