United Airlines ( UAL ) shares moved lower Friday after the carrier briefly grounded north American flights owing to a network system failure. United Airlines initiated a nationwide "ground stop" order for flights in the U.S. and Canada Friday at 6:45 am Eastern time, according to a statement from the Federal Aviation Administration, while reports of customers having issues with its consumer-facing website were reported by the internet tracking group Downdector. The ground stop was lifted at 7:30 am Eastern time, the FAA noted, and United Airlines told Reuters that its systems were now back to normal operations. United Airlines shares were marked 1.3% higher in early trading Friday to change hands at $45.05 each. United Airlines reported stronger-than-expected second-quarter revenues as "international long-haul and business travel accelerated even faster than anticipated" and as the average fares paid by passengers continued to increase.