The Federal Aviation Administration (FAA) ordered all departing flights nationwide grounded on Friday, bringing departures across the US to a halt. The move marks only the second nationwide grounding since the September 11, 2001, terrorist attacks.The FAA issued the nationwide ground stop on Friday afternoon, citing “extraordinary circumstances and for reasons of safety.”Temporary outage halts departuresThe FAA said in a post on X that a temporary telecommunications outage had prompted it to halt all flights as a precaution.“Out of an abundance of caution, all flights have been halted,” the agency said, adding that every flight had been accounted for. Inbound international flights would be handled on a case-by-case basis.US Transportation Secretary Sean Duffy had earlier said communications issues were affecting air traffic control centres across the country. FAA technicians were investigating the problem.The @FAAnews issued a nationwide ground stop for all U.S. airports following a communication issue impacting all Air Route Traffic Control Centers. FAA technicians are investigating the issue. We will provide immediate updates as we have them.— Secretary Sean Duffy (@SecDuffy) November 13, 2026A ground stop prevents aircraft from departing airports, while flights already airborne can continue to their destinations.Airlines respond to disruptionUnited Airlines said flights that were already airborne would continue, while new domestic flights would not depart as long as the FAA ground stop remained in place.The airline said it would work with customers to get them to their destinations once the issue was resolved.FAA expands new SMART systemThe disruption comes just days after the FAA announced the nationwide expansion of its Strategic Management of Airspace, Routes and Trajectories (SMART) system.The cloud-based platform brings together around 200 data streams, including weather patterns, flight paths, traffic flow and air traffic controller staffing metrics. It provides scheduling recommendations to help specialists anticipate congestion and reduce delays.The FAA said on November 10 that SMART would expand from its initial rollout in the National Capital Region to the airspace covered by all 22 Air Route Traffic Control Centers across the country.However, the agency has not linked the SMART rollout to Friday’s telecommunications outage. SMART is a traffic-planning tool and does not replace air traffic controllers or directly control aircraft.Nationwide ground stops are extremely rare. In January 2023, the FAA halted departures following an outage in its Notice to Air Missions (NOTAM) system. Before that, nationwide air traffic was halted following the September 11, 2001, terrorist attacks.