The cause of the outage is unclear, but American Airlines has told the BBC that its flights are not taking off due to an issue with Crowdstrike cybersecurity software.
The BBC reports that two hospitals in Germany has cancelled non-emergency operations
The two hospitals in the northern German cities of Luebeck and Kiel have cancelled elective operations scheduled for Friday.
Patient care and emergency services will go ahead as normal, the University Clinic of Schleswig-Holstein added.
The organising committee for the Paris Olympics says its IT operations have also been impacted.
But - with just a week to go before the Games begin - the committee says it has contingency plans, according to Reuters news agency.
- A major problem with computer systems is disrupting transport, broadcasters, hospitals and other sectors across the world
- Flights have been grounded and airports worldwide are reporting delays
- American Airlines says Crowdstrike, a cybersecurity company, is the source of the tech issues
- In the US state of Alaska, police warn the 911 system may be unavailable
- In Poland, the Baltic Hub terminal asks ships not to send their containers there
- In the UK, rail companies are "experiencing widespread IT issues" and warning of delays
- Some GP practices are struggling to access their records systems, which include online bookings
- On TV, Sky News and CBBC have been off air
While the world gets to grips with this major outage - many are left wondering how and why this has happened.
Although nothing is confirmed at this time, both Microsoft and Crowdstrike have said they are investigating issues.
Data privacy expert at law firm Gordons, Lauren Wills-Dixon, says: "We don't yet know the cause of these outages, but it appears this is linked to Microsoft and Crowdstrike which would explain disruption across sectors and globally.
"Outages can be created by several causes and Microsoft has named a 'technical issue' rather than a cyber incident.
"We'll likely find out more as the hours progress, but this shows just how reliant we are on certain tech, how much trust organisations put in them and their security practices, and also the chaos that downtime can cause."
