Update: ground stop lifted

The FAA has lifted the nationwide ground stop. The FAA Command Center announced at 01:16 UTC (20:16 in Washington) that the nationwide ground stop has been cancelled1. Departures from US airports can resume. Delta said at 21:00 Eastern time that flights have started departing, adding that it will take time to reset its operation, including the positioning of aircraft and crews. Customers can change flights at no extra cost2. The FAA said it thoroughly tested its systems to confirm they were stable before clearing flights to resume. It advised passengers to contact their airlines3. The Command Center said several local ground stops remain in place at airlines' request, with the next update on the status of the airspace system at 11:00 UTC4. Shortly before, JetBlue had cancelled its remaining Friday evening flights, except Europe-bound departures from JFK and Boston3.

At a White House briefing, Transportation Secretary Duffy said more than 3,500 aircraft were airborne when the ground stop was issued and all were brought in to land safely. Duffy said routers were overloaded with data and began to give inconsistent data, affecting radar data and communications with aircraft, after which the FAA shut the system down. He blamed an "incredibly old" air traffic control system3. Mullin said new equipment and technology being added to the system appeared to have overwhelmed the older system3. Homeland Security Secretary Mullin said there was "zero evidence" of a cyber attack and that the failure appears to have been mechanically driven, but that his department is still looking and will not rule it out3. Mullin said the public was never in danger3.

Duffy warned that the recovery will be slow and depends on crew availability. Aircraft carrying more passengers will be prioritised. Whatever cannot move tonight will be handled with the airlines on Saturday morning3.

The impact reached Europe as well. Eurocontrol suspended all US-bound departures from its 42 member states at the FAA's request. According to its notice, the suspension covered departures between 22:00 and 05:00 UTC5, a window that has now passed. Flights from the US to Europe could still operate if the FAA cleared them3.

The US Federal Aviation Administration on Friday halted all departing traffic at every airport in the United States. The FAA Command Center issued a national ground stop at 20:53 UTC (15:53 in Washington) “due to extraordinary circumstances and for reasons of safety”6. Transportation Secretary Sean Duffy said the order followed a communication issue impacting all Air Route Traffic Control Centers7. FAA technicians are investigating the issue7. In its first statement on its own website, the FAA referred to communication issues impacting multiple Air Route Traffic Control Centers8.

Latest, 22:45 UTC: the ground stop remains in effect

At 22:45 UTC the FAA Command Center said the ground stop remains in effect, citing a communications failure. As en route facilities recover, flights will be allowed to depart through coordination with the Command Center. The next update is expected at 04:00 UTC9.

Homeland Security Secretary Mullin told CNN his department is looking into whether SMART, a new AI-supported FAA route planning system, contributed to the outage3. On 10 November the FAA announced that SMART, used in the National Capital Region since September, was expanding to the airspace of all 22 centres8. ASI, the company that developed SMART, said on X that the ground stop was not based on or a result of the SMART system or any of its products3. Senator Tammy Duckworth called for a thorough and complete investigation3.

Not everything has stopped. Alaska Airlines and Hawaiian Airlines said flights within Alaska and Hawaii, flights from the West Coast to Hawaii and international flights from Honolulu can still depart, although both have cancelled and diverted some flights3. San Francisco International Airport said Pacific-bound flights have been cleared to depart3. JFK and LaGuardia airports in New York asked travellers to confirm their flight status with their airline before heading to the airport3.

What the FAA ordered

The advisory to all aircraft operators says all airports are ground stopped and all departing traffic should remain ground stopped until further notice. Inbound international flights will be managed on a case by case basis6. The advisory carries an event time until 04:00 UTC on Saturday, but its text says “until further notice”6.

Aircraft already airborne were allowed to continue to their destinations, US broadcaster WTVR reported10. In a separate advisory, the Command Center told users to expect airborne holding to any and all airports in the National Airspace System because of equipment outages, from 21:00 to 03:00 UTC11. All en route centres also extended flight plan drop times to 240 minutes “due to nationwide comms failure”, so filed flight plans stay active longer while aircraft wait on the ground12.

The Air Route Traffic Control Centers handle high-altitude traffic between airports. The FAA operates 22 of them8. According to ABC News they handle flights above roughly 18,000 feet13.

Chicago first, then the whole country

More than half an hour before the national order, Chicago O'Hare was ground stopped for departing traffic heading there. That stop began at 20:10 UTC, citing an equipment outage with the comment “comms issues”14. Chicago Midway followed at 20:17 UTC, also citing an equipment outage15.

FAA: a temporary telecommunications outage

About an hour after the announcement, the FAA said the nationwide ground stop was caused by a “temporary telecommunications outage”. The agency said that “out of an abundance of caution all flights have been halted” and that all flights have been accounted for3. Homeland Security Secretary Markwayne Mullin told reporters at the White House there was “no indication as of yet that this was a nefarious attack against us”. He said he would not rule out any cause, including a cyber attack3. Mullin said the outage is not connected to Thursday's global Microsoft outage3. No timeframe has been set for the repair. “This isn't going to just be resolved and turned around within the hour”, Mullin said3.

What is not yet known

The FAA and the Department of Transportation have not yet said which routers were overloaded or why3. The FAA has not yet said how many flights are affected.

Flights to and from Europe

Because the order covers all departing traffic from US airports, evening and overnight departures to Europe fall under it for as long as it lasts6. International flights are being handled case by case, however: CNN reported that a Lufthansa flight from Chicago O'Hare to Frankfurt was cleared for takeoff on Friday evening3. Flights from Europe to the United States are being managed case by case6. United Airlines told passengers in its app that it is holding planes from taking off while the ground stop is in place and that flights already in the air will continue3. Southwest Airlines told employees it is working with the FAA towards a resolution3. Delta said no Delta flights are departing while the ground stop is in effect, flights en route will continue. A travel waiver is in place so customers can change their flights16. JetBlue has temporarily suspended all departures3. American Airlines said its flights are expected to be disrupted for the rest of the day, depending on how long the ground stop lasts3. American has waived change fees for customers booked to travel on 13 or 14 November who can travel by 17 November17. Industry group Airlines for America encouraged affected travellers to stay in touch with their carrier for real-time updates3. During the January winter storm the FAA advised travellers to check flight status with their airline and to follow real-time airport status at nasstatus.faa.gov8.

How a ground stop works

Under FAA rules a ground stop is one of the most restrictive forms of traffic management: aircraft that meet specific criteria must remain on the ground. A ground stop overrides all other traffic management initiatives. Aircraft must not be released without the approval of the facility that issued it18. A ground stop can cover one airport, a block of airspace or specific aircraft, for example during severe weather or a runway closure. Ground stops normally occur with little or no warning18. Friday's national stop was issued by the FAA Command Center6.

Earlier national ground stops

Nationwide ground stops are rare3. On 11 September 2001 the FAA Command Center ordered a nationwide ground stop at 09:25 Eastern time. At 09:42 it ordered all aircraft to land at the nearest airport, an unprecedented order. About 4,500 aircraft landed without incident19.

On 11 January 2023 the FAA ordered airlines to pause all domestic departures until 09:00 Eastern time after an outage of the NOTAM system20. The ground stop was lifted at 08:5020. A preliminary FAA review later found that contract personnel had unintentionally deleted files, with no evidence of a cyber attack20.

This article will be updated as the FAA and airlines release more information.