This is a worldwide outage.
American, Delta, United and Ryanair are experiencing delays.
Berlin, Amsterdam Schipol, Manchester (UK), Gatwick and Standsted are some of the airports around the world experiencing serious delays.
The NHS in the UK as well as the Emergency Broadcast System in the US are having problems.
The cause is an issue with a software upgrade at Crowdstrike-a large cybersecurity company used by these companies and institutions as well as banks. There are no reports of a cyberattack.
UPDATE: Many European airlines are experiencing some delays including online check in.
UK Trains are operating but experiencing cancellations.
Crowdstrike now says a fix has been issued but it will take awhile for things to get back to "normal."
If you are traveling today, give yourself extra time.