CHICAGO, Illinois: United Airlines said this week that a software update, which led to a widespread slowdown in its technology systems, caused an hour-long nationwide ground stop.

United is "investigating the cause, but it was not a cybersecurity issue," the airline said, adding the issue did not affect flights already in the air.

The Federal Aviation Administration (FAA) earlier said that it issued the ground stop at the request of the Chicago-based airline.

According to the FAA and United, the ground stop lasted just over an hour and ended at 1:45 p.m. EDT (1745 GMT).

On September 5, United canceled seven flights and delayed 364, or 13 percent of its flights, according to flight tracking website FlightAware.