• Air travel in the US is snarled after a global IT outage.
  • A map shows air traffic grinding nearly to a halt during a normally busy early morning period.
  • Major US airlines were resuming flights Friday after grounding planes because of the IT issue.

Friday's IT outage caused widespread disruptions after Microsoft reported problems with its online services, linked to an issue at cybersecurity firm CrowdStrike.

But it had one of its most dramatic effects on US commercial flights.

A time-lapse map shared by Colin McCarthy on X, formerly known as Twitter, using flight tracking website Flightradar24.com shows flights grinding to a halt overnight in the US.

The map appears to start around UTC 00:00 on Friday — or 8 p.m. Eastern Time on Thursday — and shows air traffic for Delta Air Lines, United Airlines, and American Airlines flights slowing down late into the night. Business Insider verified the map using Flightradar24's playback feature.

But as the sun rises and time reaches UTC 12:00 — or 8 a.m. ET on Friday — air traffic for the three major US airlines doesn't pick up. Early mornings on weekdays tend to be busy travel times at US airports.

US flight cancellations started early Friday morning, according to data from Cirium, an aviation analytics company.

Airlines had canceled nearly 1,700 flights — or 6.3% of their scheduled US service for the day — as of 11 a.m. ET, Cirium reported. That number had grown from about 500 cancellations at 6 a.m. ET.

Thirty-seven percent of US flights on Friday departed after a delay of at least 30 minutes, Cirium also said.

Delta, United, and American all issued ground stops for their flights early on Friday. American and Delta have started lifting the stop orders, allowing some flights to take to the skies.

The map from McCarthy and Flightradar24 appears to show a pickup in departures near 8 a.m. ET.

United and American warned pilots in the air that the IT glitch was affecting communication between their aircraft and people on the ground, including air traffic control and the airlines themselves.

The IT problem, which has affected everything from banks to hospitals, affected flights worldwide.

Passengers in airports from the UK to Thailand waited to learn whether their flights would depart, with airport and airline staff directing passengers to check Google, not airport monitors, for the status of their flight or issuing hand-written boarding passes.

The CrowdStrike update that led to the problems affected devices that use Microsoft's Windows operating system.

Read the original article on Business Insider