CHICAGO (AP) United Airlines says a 'network connectivity issue' is to blame for the problem that grounded flights nationwide.
The airline says in a statement that it's in the process of resuming normal operations on Saturday following the outage Friday night.
United said flight operations will be affected throughout the weekend.
The problem lasted for about five hours on Friday night, and left some people scrambling to make new arrangements. Some slept in airports or found hotel rooms in cities where they were stranded.
Long lines of passengers formed at airports in San Francisco, Los Angeles, Denver and Chicago.
United apologized for the disruption and says customers who were inconvenienced should contact the airline.