NEW YORK -- Major websites went down Thursday in what appeared to be a brief but widespread outage.

       The websites of Airbnb, AT&T, Costco and Delta showed error messages around midday Eastern time. They seemed to be operating normally, however, by 12:45 p.m.

       Akamai, a major behind-the-scenes internet network company, said the disruption lasted about an hour and that it was due to a software update in the system that directs browsers to websites. It said there was no cyberattack.

       The company said it was reviewing how it updates software to try to prevent outages in the future.