Microsoft outage causes mass airline disruptions. Here's what to know.

Air travel is experiencing disruptions across the globe on Friday morning due to a Microsoft outage for customers of its 365 apps, including many major airlines.

In the U.S., more than 1,300 flights had been canceled as of 10 a.m. Eastern Time, while more than 3,600 flights have been delayed, according to FlightAware, a flight tracking service.

Airlines said the outage impacted the back-end systems they use to send key data, such as weight and balance information, required for planes to depart.

Air travelers posted images on social media of long lines at ticket counters, and "blue screens of death" — the Microsoft error page when its programs aren't working — at screens at various airports. The issue was caused by a software update sent from cybersecurity firm CrowdStrike to Microsoft, and which it said it had identified in its systems and was working to resolve.

"In a nutshell, this is PR nightmare for CrowdStrike and Microsoft and others get caught in this tornado along with millions of people currently stranded at airports around the globe," Wedbush analyst Dan Ives said in a report.

Travelers in Europe are also facing disruptions, with Lufthansa, KLM and SAS Airlines reporting issues. Switzerland's largest airport, in Zurich, said planes were not being allowed to land, according to CBS News partner network BBC News.

In Australia, airline Jetstar canceled all flights from the Brisbane airport for the day, according to the BBC. One traveler in Scotland told The Guardian she paid $8,600 for new tickets back to the U.S. after her original flight was canceled due to the IT outage.

Delta Air Lines

At about 7:50 a.m. Eastern Time, Delta said it resumed some flights after an airline-wide pause earlier on Friday morning due to the Microsoft outage. Delta had canceled about 450 U.S. flights as of 10 a.m., FlightAware data shows.

"We are working to resolve the issue as quickly as possible to resume operations," Delta said in its statement.

United Airlines

United said it has been able to resume some flights, but warned customers to "expect schedule disruptions to continue throughout Friday." About 220 United flights had been canceled as of 10 a.m. ET Friday morning, although some flights left from Newark airport this morning.

The airline added, "We have issued a waiver to make it easier for customers to change their travel plans via United.com or the United app."

American Airlines

American said it has restarted its operations at about 5 a.m. Eastern Time. FlightAware data shows that about 300 American flights had been canceled as of roughly 10 a.m.

Alaska Airlines, Southwest, Frontier

Alaska Airlines told CBS News that is functioning normally. Southwest and Frontier also appear to be operating normally.

—With reporting by Kris Van Cleave.