Airports across the US slowly descended into chaos on Friday morning after a worldwide tech outage disrupted flights and stranded passengers.

More than 650 flights across the country were delayed and more than 100 others were cancelled, according to FlightAware, a database that tracks flight information. Airports in the New York City and Chicago regions appeared to be hardest hit.

As the sun rose over the East Coast, at least five airlines — Allegiant Air, American, Delta, Spirit and United — had issued ground stops, according to the Federal Aviation Administration.

“The FAA is closely monitoring a technical issue impacting IT systems at US airlines,” the agency said. “Several airlines have requested FAA assistance with ground stops for their fleets until the issue is resolved.”

It was unclear how long the ground stops were expected to last, but it was causing some headaches for travellers.

American Airlines said in a statement on social media on Friday morning that it was aware of a tech issue with its vendor affecting multiple carriers.

Similarly, Delta said in a statement that it had “paused” flights and United Airlines warned customers that delays may linger throughout the day. At Denver International Airport, large screens typically used to detail flight arrivals and departures were flashing blue error messages, leaving some passengers confused.

Frank Tingley, a 42-year-old data analyst, was among thousands of travellers stranded at that airport.

“I’m not good, actually,” he said, adding that he first noticed an issue when airport staff had difficulties scanning tickets. Tingley said he was initially allowed to board the plane but later passengers deplaned. “The general mood is that people are finding a quiet corner and just trying to hunker down,” he said.

New York Times News Service