A number of main web sites briefly go down in widespread web outage

Several major websites briefly went down on Thursday in a widespread outage linked to content distribution network Akamai. By about 12:50 p.m. Eastern Time, Akamai said it fixed the issue and the service seemed to be back to normal.

Akamai, a CDN, which helps data move around the internet, said on its website earlier on Thursday that it was investigating “an emerging issue with the Edge DNS service.”

Oracle, a cloud service provider, had also pointed to Akamai as the source of the issue which impacted some Oracle cloud properties. But Oracle said resources within its own cloud service are not impacted by the incident.

The Domain Name System is like a phone book for websites. The technology figures out the right IP addresses to use when people try to go to individual websites. The Edge DNS service from Akamai takes care of this work for apps and websites and protects against distributed denial-of service, or DDoS, attacks.

Delta Air Lines, British Airways, Capital One, Go Daddy, Vanguard, UPS, LastPass, AT&T and Costco were among the websites loading slowly or showing “DNS failure” Thursday early afternoon.

The outage meant airline customers impacted by the outage were briefly prevented from checking in for flights or looking up fares online, meaning they would have to check in at the airport.

This is breaking news. Please check back for updates.

-CNBC’s Leslie Josephs and Jordan Novet contributed to this report.