The Federal Aviation Administration ordered a nationwide ground stop on all departing flights Friday afternoon. According to reports from NBC News, the FAA says the order happened because of “extraordinary circumstances and for reasons of safety.” US Secretary of Transportation Sean Duffy added that a “communication issue impacting all Air Route Traffic Control Centers.” The order was lifted at approximately 8:15 pm ET on Friday after systems were tested and confirmed stable, though lingering delays and cancellations continued. Pittsburgh International Airport listed delays for at least 43 flights with at least four flights canceled.