A massive technology outage has disrupted businesses and institutions in multiple countries, throwing airports, airlines, rail companies, government services, banks, stock exchanges, supermarkets, telecoms, health systems and media outlets into chaos. The cause of the outage was not immediately clear, but it came hours after Microsoft said it was addressing an issue affecting access to Microsoft 365 apps and services. Some experts attributed the disruption to CrowdStrike, a cybersecurity firm whose software is used by industries around the world to protect against hackers and outside breaches. The problem appeared to result in crashes of machines running the Microsoft Windows operating system. CrowdStrike said in a recorded phone message that it was aware of reports of Microsoft’s Windows operating system crashing. Reporting from London, Al Jazeera’s Jonah Hull said, “CrowdStrike seems to have had some sort of mandatory update to its software that went horribly wrong.” The company had reported that the issue was related to its Falcon sensor product, engineers identifying a “content deployment problem”, said Hull. “It has been a quite extraordinarily dysfunctional, disruptive morning from an IT point of view – or indeed mid-afternoon if you’re in Australia where the first signs of a real problem began to emerge, according to Hull. “Essentially it happens as you’re sitting in front of your terminal. If your terminal is a Microsoft Windows terminal, it suddenly goes to a blank blue screen. It’s called the ‘blue-screen-of-death’ error. You are locked out of your operating system,” Hull said. At the time of reporting, some of the malfunctioning business, companies and computer app systems were beginning to return to normal service, including Sky News in the United Kingdom, which was down for an hour in the morning. The outages rippled far and wide, with transport systems around the world among the hardest hit. In the United States, major airlines Delta, United and American Airlines were grounded on Friday morning due to a communication issue, according to an update by the Federal Aviation Administration. In Australia, flight information screens at Sydney airport went blank. The airport said that flights were arriving and departing but that travellers should expect delays. “We have activated our contingency plans and deployed additional staff to our terminals,” it said in a post on X. Melbourne airport said that check-in procedures for some airlines had been affected. “Passengers flying with these airlines this afternoon are advised to allow a little extra time to check-in. Please check with your airline for flight updates,” it said in a post on X.