The United States is struggling to restore normal air travel after its most serious nationwide flight grounding in 25 years, with thousands of passengers stranded at airports, hundreds of aircraft out of position and airlines warning that disruption could last for several days.
Despite the lifting of the nationwide departure ban, major problems persisted on Saturday morning, 14 November.
According to the latest available figures from flight-tracking platform FlightAware, more than 8,860 flights to, from or within the United States were cancelled on Friday, with another 2,650 cancellations already recorded for Saturday, bringing the total to more than 11,500.
The figures continue to change, and not all cancellations can necessarily be attributed solely to Friday’s technical failure.
Nevertheless, the scale of the disruption illustrates the knock-on effects of the Federal Aviation Administration’s (FAA) decision to suspend departures nationwide for more than four hours.
Domestic and international flights have been affected, with disruption extending to airports in Canada and Mexico as US airlines work to reposition aircraft and crews.
The incident has also exposed the dependence of the world’s largest aviation network on ageing communications infrastructure, some of which relies on technology dating back to the 1980s.
The US government confirmed that the failure was linked to overloaded telecommunications equipment, although investigators have yet to establish what triggered the initial malfunction.
Fresh cancellations on Saturday leave passengers stranded
Airlines are struggling to accommodate passengers whose flights were cancelled or rescheduled across major US airports, including Dallas, Chicago, New York and Los Angeles.
Some travellers spent hours aboard aircraft waiting to take off or secure a gate after landing. Others were forced to look for hotel accommodation when their flights were cancelled without immediate alternatives.
At Dallas airport, a mother and her 14-year-old daughter waited more than four hours for a flight to Ohio, where the teenager had planned to surprise a friend.
They eventually abandoned the trip without knowing when they would be able to travel.
In Los Angeles, passengers arriving on a flight from Newark remained aboard their aircraft for more than five hours after landing because no gate was available.
Similar scenes unfolded in Charlotte, North Carolina, where passengers spent hours on the tarmac before seeking alternative transport.
Airlines have begun restoring services, although the recovery has been uneven.
Delta, United and American Airlines said they were gradually rebuilding their schedules, while JetBlue cancelled a large proportion of its Friday evening flights and planned to resume services on Saturday.
Airlines have also introduced special ticket-change arrangements for affected passengers.
Why reopening US airspace is not enough
The biggest challenge for airlines is that the nationwide departure suspension disrupted the schedules of thousands of flights.
Aircraft typically operate several services each day. A plane leaving New York in the morning, for example, might be scheduled to complete another two or three flights before the evening.
When that aircraft remains grounded for several hours, the entire sequence of flights is disrupted.
The same problem applies to crews, who must comply with strict limits on working hours and mandatory rest periods.
Even when an aircraft is technically ready to depart, its flight may be cancelled because the pilots or cabin crew have reached their permitted working limits.
Passengers missing connecting flights, aircraft diverted to airports outside their planned routes and limited availability on subsequent flights add further pressure.
These disruptions explain why a shutdown lasting just over four hours can affect aviation operations for days.
US Transportation Secretary Sean Duffy acknowledged that restoring normal operations would take time.
“We’re going to need time to untangle what happened,” he said, noting that the ability to operate flights now depended on aircraft and crew availability.
The US government expects the aviation network to return to normal before the Thanksgiving travel period, although officials have not specified exactly when all scheduled services will be restored.
How aircraft were grounded across the United States
The crisis began on the afternoon of Friday, 13 November.
At 3.36 pm Eastern Time, US authorities detected instability in communications systems and radar data used by regional air traffic control centres.
The problem affected the 22 control centres responsible for managing flights across US airspace, as well as facilities monitoring aircraft approaching and departing major airports.
Shortly before 4 pm, the FAA issued a nationwide ground stop, citing emergency circumstances and safety concerns.
The order required aircraft on the ground to remain there until further notice.
Flights already airborne continued to be monitored and directed towards safe landings, while international flights were assessed individually.
According to aviation data company Cirium, approximately 11,000 departures carrying more than 1.5 million scheduled passengers remained on the day’s flight programme when the crisis began.
By 7.05 pm Eastern Time, at least 827 flights had either been diverted or forced to return to their departure airports.
Of those, 670 returned to their original airports, while 157 landed elsewhere.
The grounding lasted more than four hours, until 8.15 pm, when authorities announced that the systems had stabilised and departures could gradually resume.
Technical failure exposes ageing US aviation infrastructure
The US government’s explanation for the disruption has drawn attention to failures involving outdated telecommunications equipment.
During a White House briefing, Duffy said network switches and data routers had become overloaded, causing instability in the transmission of critical information.
He described an extremely old air traffic control system that continues to rely on analogue technology and copper telecommunications lines installed decades ago.
At the centre of the problem is a technology known as time-division multiplexing (TDM), which allows multiple signals to be transmitted over shared communications lines.
Although TDM has been used for decades, significant sections of the US aviation communications network continue to depend on it.
According to Duffy, the overload caused inconsistencies in the information received by air traffic controllers.
Technicians eventually restored operations by reducing pressure on the networks, carrying out technical interventions and re-establishing communications.
However, the precise cause of the initial overload has not been conclusively established.
The failure has raised concerns because the affected technology remains part of critical national infrastructure supporting tens of thousands of flights every day.
Duffy himself could not guarantee that a similar malfunction would not happen again.
Questions over artificial intelligence and possible cyberattack
The timing of the technical failure has also prompted questions about a new artificial intelligence-based air traffic management system whose expansion the FAA announced only days earlier.
The SMART programme, developed by Air Space Intelligence, was designed to improve flight planning and help controllers identify more efficient routes.
Its expansion to the 22 regional air traffic control centres was announced on 10 November, prompting questions about whether it could be connected to Friday’s disruption.
However, both the company behind SMART and the US transportation secretary denied that the system was responsible.
Duffy said the new equipment had operated normally and that the failure had occurred within older telecommunications networks.
Authorities are also examining the possibility of malicious interference.
Homeland Security Secretary Markwayne Mullin said there was no evidence of a cyberattack so far.
He added, however, that the investigation was continuing and that officials could not yet rule out every possible cause with absolute certainty.
The US government said passenger safety had not been compromised and that more than 3,000 flights landed safely during the departure suspension.
Flight disruption hits sports teams across the country
The effects of the nationwide grounding extended beyond ordinary passengers, disrupting travel arrangements for NBA and NHL teams and college American football programmes preparing for weekend fixtures.
Auburn University was forced to arrange bus transport for its football team to Mississippi, while the start time of its game against Mississippi State was postponed.
Teams from universities in Washington, Texas and other states faced similar problems, prompting competition organisers to consider schedule changes.
Duffy urged teams experiencing significant travel difficulties to contact the FAA so that possible arrangements could be considered.
International air travel was also affected, with Air Canada cancelling flights between Canada and the United States, while services to Mexico experienced disruption.
$50 billion aviation upgrade under discussion
The crisis has renewed political debate in Washington over funding for the US air traffic control system.
Duffy argued that ageing infrastructure could no longer safely meet the growing demands of air travel without a comprehensive technological overhaul.
Congress has already approved $12.5 billion for modernisation projects, while the administration has requested approximately $30 billion in additional funding.
Following Friday’s failure, Duffy called for total funding of approximately $50 billion.
The proposed upgrades would replace outdated communications equipment, modernise control centres and introduce advanced digital networks.
Modernisation is already under way, but replacing existing systems is a complex process because air traffic operations must continue without interruption during the transition.
Friday’s nationwide failure demonstrated the potentially far-reaching consequences of a malfunction affecting a critical part of the network.
Unanswered questions after the biggest shutdown since 2001
The grounding was the longest nationwide suspension of departures in the United States since the September 11, 2001 terrorist attacks.
The previous comparable incident occurred in January 2023, when the FAA temporarily suspended departures following a failure of the Notice to Air Missions (NOTAM) system, which provides pilots with essential flight information.
Friday’s shutdown lasted more than four hours and caused considerably greater disruption to air travel.
The challenge now extends beyond accommodating stranded passengers and restoring normal airline schedules.
The US government also faces questions about how one of the world’s most important transport networks proved so vulnerable to a failure involving ageing equipment, and what measures can prevent another nationwide shutdown before modernisation is completed.
Read more: US lifts nationwide flight ban after communications failure disrupts air traffic control (updated)
