NEW YORK CITY (WABC) -- Thousands of flight delays and cancellations rippled across the U.S. early Wednesday after a computer outage led to a grounding order for all departing aircraft by the Federal Aviation Administration.
The delays cascaded into the evening from coast to coast. The nationwide ground stop was the first since 9/11.
The ground stop and FAA systems failures Wednesday morning appear to have been the result of a mistake that occurred during routine scheduled systems maintenance, according to a senior official briefed on the internal review.
An engineer "replaced one file with another," the official said, not realizing the mistake was being made Tuesday. As the systems began showing problems and ultimately failed, FAA staff feverishly tried to figure out what had gone wrong. The engineer who made the error did not realize what had happened.
Had the FAA's new NOTAM system been in place, redundancies would likely have stopped the cascading failures. With the antiquated system in place, there was nothing to stop the outages.
"It was an honest mistake that cost the country millions," the official said.
It was all over by 9 a.m., but the damage was done. As of Wednesday evening, more than 9,000 domestic flights had been delayed, according to the flight tracking service FlightAware. There were 1,300 cancellations domestically.
The impact was felt by travelers across the Tri-State area.
Gates at JFK were packed with confused passengers and 33% of flights were delayed.
It was a similar scene at LaGuardia, where 46% of flights were delayed.
And the domestic terminal at Newark Liberty International didn't start to empty out until shortly before noon, as passengers waited for later departures or deal with cancellations. Newark saw 29% of flights delayed.
Several airlines scrambled to address customers' frustrations.
United Airlines, which has a hub at Newark Liberty International Airport, and which paused all flights ahead of the FAA's nationwide ground stop order, issued travel waivers to passengers who were impacted.
Experts say for decades, the NOTAM system has never really failed. Airline business expert David Slotnick says there's a good reason it has never been replaced.
"When something works, they don't change it unnecessarily because any kind of change has to be done slowly deliberately and purposefully to avoid any kind of safety hazard," said Slotnick.
This is just the latest headache for travelers in the U.S. who faced flight cancellations over the holidays amid winter storms and a breakdown with staffing technology at Southwest Airlines.
They also ran into long lines, lost baggage, and cancellations and delays over the summer as travel demand roared back from the COVID-19 pandemic and ran into staffing cutbacks at airports and airlines in the U.S. and Europe.
To check if your flight has been impacted, here are links to the websites for the three major airports in the Tri-State area:
The Associated Press contributed to this report.