Airlines, passengers, and businesses worldwide struggled to overcome significant disruptions after a massive global IT outage linked to the U.S. cybersecurity company CrowdStrike caused unprecedented havoc.

Airports from Berlin and Zurich to New Delhi and Sydney were among those thrown into disarray after a bug in a CrowdStrike update affected computers running Microsoft Windows software.

"This is not a security incident or cyberattack. The issue has been identified, isolated and a fix has been deployed," CrowdStrike boss George Kurtz posted on social media platform X.

Kurtz later told U.S. broadcaster NBC: "We fixed it on our end."

He added that the company is "deeply sorry" for the difficulties it has caused "to customers, to travelers, to anyone affected by this."

A spokesperson for software giant Microsoft said the company was "aware of an issue affecting Windows devices due to an update from a third-party software platform."

Later on Friday, Microsoft suggested that businesses running its Azure cloud computing platform should attempt to reboot their systems, with some reporting up to 15 reboots were required.

Passengers across the world have faced huge disruptions to their travel plans, with many airlines reporting difficulties with check-in.

In the United States, major airlines United, American and Delta have all resumed operations, but warned of delays and cancellations after the Federal Aviation Administration (FAA) earlier ordered their flights to be grounded.

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

Parcel delivery firm FedEx said it faced substantial disruptions throughout its networks, while peer United Parcel Service also warned of potential delivery delays.

European budget airline Eurowings said on X that it would operate 80% of its scheduled flights, canceling a number of domestic German services.

Dutch carrier KLM said that "limited air traffic" would resume after largely suspending operations earlier on Friday.

Zurich Airport, which earlier said it would restrict landings, said at least 100 departures and arrivals have had to be canceled.

Berlin's BER airport was particularly affected, with all flights grounded early on Friday. Operations slowly began returning to normal around midday.

Türkiye's national flag carrier Turkish Airlines said it was "experiencing problems with ticketing, check-in, and reservation processes" in a post on social media platform X.

The company said it had canceled around 84 flights scheduled for Friday.

At Sydney Airport, passengers were told they could not check in luggage, with domestic and international flights affected.

In India, boarding passes were being filled out manually as check-in was disrupted at New Delhi's main airport.

Contingency plans were also in place at Heathrow Airport in London, the airport said, advising passengers to continue checking the status of their flights.

The global IT outage has caused difficulties across a wide range of sectors on Friday, from media outlets to payments at shops and doctor's offices.

In the U.K., broadcaster Sky News was back on air after being knocked off the air for hours, while several television channels in France were also affected.

Australian radio stations reportedly broadcast music via CDs and USB sticks after computer systems went down.

Emergency services were hit in Denmark, with the Copenhagen fire department reporting problems with receiving automatic fire alarm warnings.

The healthcare sector has also been affected, with pharmacies and doctor's offices reporting tech and payment problems across Britain.

In northern Germany, the University Hospital Schleswig-Holstein said it was canceling all planned operations at its facilities in the cities of Kiel and Lübeck.

Australian banks were also said to be struggling to deal with the IT outage. In response, Australian Prime Minister Anthony Albanese convened an emergency meeting.

The global outage is likely to have serious economic consequences, with angry passengers and businesses sure to demand how an update to a largely unknown security company could leave international aviation grounded and IT systems down.

Nevertheless, it appears that critical systems across the globe escaped unharmed.