A global tech outage was disrupting operations in multiple industries on Friday, with airlines halting flights, some broadcasters off-air and everything from banking to health care hit by system problems.

According to an alert sent by global cybersecurity firm Crowdstrike to its clients and reviewed by Reuters, the company’s Falcon Sensor software is causing Microsoft Windows to crash and display a blue screen, known informally as the “blue screen of death.”

The problem crashed Windows machines and servers, sending them into a loop of recovery so that they couldn’t restart.

“CrowdStrike is actively working with customers impacted by a defect found in a single content update for Windows hosts,” company CEO George Kurtz said in a message posted on social media. “Mac and Linux hosts are not impacted. This is not a security incident or cyberattack. The issue has been identified, isolated and a fix has been deployed.”

“We’re deeply sorry for the impact that we’ve caused to customers, to travellers, to anyone affected by this, including our company,” Kurtz said in an interview with NBC’s morning news program Today.

Kurtz said that while some systems won’t automatically recover, the company would “make sure every customer is fully recovered.”

The issue affected Microsoft 365 apps and services. The website DownDectector, which tracks user-reported internet outages, recorded growing outages in services at Visa, ADT security and Amazon, as well as airlines.

Microsoft said on Friday that the underlying cause for outage of its 365 apps and services has been fixed, but the residual impact of cybersecurity outages are continuing to affect some customers.

Scale of outage concerns experts

Even as companies and institutions began restoring regular services, experts said the cyber outage revealed the risks of an increasingly online world.

“This is a very, very uncomfortable illustration of the fragility of the world’s core internet infrastructure,” Ciaran Martin, professor at Oxford University’s Blavatnik School of Government and former head of the U.K. National Cyber Security Centre, told Reuters.

“I’m struggling to think of an outage at quite this scale,” said Martin.

Ritesh Kotak, cybersecurity and tech analyst, told CBC News Network that clients and consumers will have to be patient.

“A lot of these systems have redundancies that are built into them. So, for example, when one system fails, it can piggyback off another system; it just literally passes the baton,” said Kotak.

“It’s not as smooth sometimes as one may think … but depending on the scale of the servers impacted sometimes it takes just a little bit of time to pass over that baton and then fix the problem and then bring those services back on to the original servers.”

Several airlines affected

Airline traffic was especially affected, though the impacts were variable. A spokesperson from Toronto’s Pearson Airport told CBC News the impacts varied “airline to airline.”

“As of now, Air Canada, Westjet, Sunwing and Flair operations have not been affected. We’re still seeing issues with major American airlines (Delta, American, United) as well as Porter Airlines,” Pearson said in a separate statement.

Porter Airlines, which operates flights across Canada and to some U.S. locations, said all flights would be cancelled until at least 3 p.m. on Friday. The company said just after 6 a.m. that its call centre agents did not have access to reservation or rebooking information, and it’s directing customers to its website for updates.

“Any passengers needing to cancel travel plans as a direct result of the systems issue will be offered refunds,” said Porter. “Normal flight change fees are also being waived.”

Representatives from the international airports in Montreal and Vancouver told CBC News that U.S. customs officials could not process passengers heading to American destinations.

Montreal-Trudeau International Airport said “the problem has been resolved and passenger processing is gradually resuming.”  U.S. Customs and Border Protection released its own statement indicating the issue, related to the global Crowdstrike outage, had been resolved.

Airports across Canada have advised customers travelling or doing pickups of family and friends to check flight status with the airlines before heading out.

Traffic delays at points of entry on land between Canada and the U.S. were also reported.

The Canada Border Services Agency (CBSA) said in a statement that it had experienced a partial systems outage of its telephone reporting system that was subsequently resolved. The statement did not make reference to Crowdstrike and Microsoft issues.

In the U.S., the Federal Aviation Administration said the airlines United, American, Delta and Allegiant had all been grounded. Some travellers at Los Angeles International Airport slept on a jetway floor, using backpacks and other luggage for pillows.

More than 1,400 flights were cancelled across the U.S., with nearly 4,000 delayed, as of 10:00 a.m. ET on Friday, according to data tracker FlightAware.

Delta and United said they were resuming some flights but expected additional delays and cancellations. The airlines also issued travel waivers for impacted passengers.

Internationally, airports from Britain to India and Hong Kong reported delays, with some resorting to manual check-ins.

French airports said the issues were airline-specific and the Paris Olympics organizing committee said on Friday the impact of the global outage on its operations was limited and ticket sales were unaffected ahead of the Summer Games, to begin in one week.

Private, public sector issues

CrowdStrike says it has more than 20,000 subscription customers around the world, with over half of Fortune 500 companies using its sofware, according to company promotional materials from this year.

As a result, a number of companies across sectors were affected.

FedEx Corp said on Friday it experienced substantial disruptions to deliveries throughout its networks.

“Contingency plans have been activated to mitigate impacts but potential delays are possible for package deliveries with a delivery commitment of July 19,” FedEx said.

The CBC experienced some issues with automated broadcasting processes, affecting control room operations, cameras and graphics, that were resolved after a few hours.

Some Canadian and international health-care providers and clinics reported issues with accessing appointment and patient record systems.

Crowdstrike shares were down about 10 per cent as trading began Friday in North America.