The FAA said Wednesday evening that a "damaged database file" was the root cause of a systemwide failure in its NOTAM safety information database, which grounded flights across the US for several hours that morning. There was "no evidence of a cyberattack," according to the agency.

The ground stop was issued early Wednesday morning, shortly after the NOTAM - or Notice to Air Missions - system crashed, halting departures nationwide even as the airways recover from mass cancellations at Southwest Airlines over the holidays. Flights resumed later in the morning.

A report from ABC news said that the NOTAM crash was caused by an engineer's error during overnight maintenance, citing unnamed officials as saying that the worker simply "replaced one file with another."

That report said that the error was made during routine maintenance and would not have happened if the agency's new NOTAM system had been fully in place at the time. The FAA has been working for years to modernize the NOTAM system, which provides a standardized database of up-to-date advisories about flying conditions and potential delays to all pilots, and is a critical source of safety data for US airlines.

The agency's plans for the NOTAM upgrade date back to at least 2018, and the FAA has sunsetted two older programs - Notice to Airmen Publications or NTAP, and PilotWeb - in favor of a centralized, searchable website for safety information. APIs are available for developers to build out their own information systems and policy changes have been put in place to reduce the number of permanent NOTAMs that pilots are required to read.

The pace of change may increase, as legislators eye responses to the outage. Senator Maria Cantwell, a Democrat from Washington and the chair of the Committee on Commerce, Science and Transportation, tweeted yesterday that lawmakers "will be looking into what caused this outage and how redundancy plays a role in preventing future outages."

"The public needs a resilient air transport system," Cantwell said.

Speaking to the Associated Press, a former American Airlines executive and consultant, Tim Campbell, said that the outage lends weight to the concerns raised by many stakeholders about the FAA's overall technology base.

"So much of their systems are old mainframe systems that are generally reliable but they are out of date," he said.