US FAA grounds flights nationwide for second time since 9/11: What caused the disruption as 10,000 flights face delays?

The FAA grounded US flights nationwide after a telecommunications outage disrupted air traffic control centres. More than 10,000 delays were reported, with cancellations and diversions mounting. This was the second nationwide ground stop since 9/11.

The US aviation system faced an unprecedented disruption after the Federal Aviation Administration (FAA) ordered a nationwide ground stop on Friday, halting departing flights at airports across the country because of a communications outage affecting air traffic control centres, AP reported.

The disruption affected thousands of flights, leaving passengers stranded at airports, forcing airlines to divert aircraft and disrupting international travel. Cargo operations and professional sports teams travelling for weekend fixtures were also caught up in the stoppage.

This was the second time since the September, 2001 (9/11) terrorist attack that flight operations across the country has been halted. Another nationwide outage was reported in 2023.

Quick answers to key questions

The FAA attributed the disruption to a temporary telecommunications outage affecting air traffic control operations at 22 centres. The exact cause was not established; reports said a network update may have triggered a reboot, while authorities reported no indication of a deliberate attack.

FlightAware reported more than 10,000 delays and over 4,000 cancellations. Cirium reported at least 600 diversions by 5:50 pm Eastern Time, including 496 flights sent back to their departure airports.

No. Flights that were already airborne continued to their destinations, with authorities coordinating their safe landing. FlightRadar24 estimated that around 3,100 aircraft were headed to US airports when the stop began.

At the FAA's request, Eurocontrol suspended US-bound departures from its 42 member states until midnight Eastern Time. Mexico's aviation agency also grounded scheduled flights departing for the US.

Yes. Air India advised passengers to check their flight status before travelling to the airport, as the ground stop caused delays, cancellations and diversions.

The FAA said the decision was taken as a precaution to ensure flight safety while technicians investigated the problem. Here is what happened, how many flights were affected and what authorities have said about the cause.

According to multiple reports, the problem stemmed from a telecommunications outage affecting the 22 air route traffic control centres that manage aircraft travelling between airports across the US.

Transportation Secretary Sean Duffy said FAA technicians were investigating the communications issue. The agency subsequently said all flights had been accounted for and that international departures would be handled on a case-by-case basis.

The ground stop did not mean that aircraft already flying were ordered to land immediately. Flights that were airborne continued towards their destinations, with authorities coordinating their safe landing.

According to aviation analytics company Cirium and cited by AP, at least 600 flights had been diverted as of 5.50 pm Eastern Time on Friday.

Of these, 496 flights were sent back to the airports from which they had originally departed, while 104 were diverted to alternative airports. Chicago O'Hare International Airport, Denver International Airport, Dallas Fort Worth International Airport and Ronald Reagan Washington National Airport were among the airports receiving diverted aircraft.

The scale of the disruption was expected to increase. Around 11,000 flights carrying more than 1.5 million passengers had been scheduled to depart US airports after 4 pm Eastern Time on Friday.

Flight-tracking website FlightAware also reported more than 10,000 delays and over 4,000 cancellations within a short period of the disruption.

FlightRadar24 estimated that around 3,100 aircraft were airborne and headed towards US airports when the ground stop began.

What caused the nationwide flight disruption?

The FAA initially attributed the ground stop to a temporary telecommunications outage affecting air traffic control operations. However, the exact cause of has not established as of yet.

A CBS News report, citing multiple sources, said an update to the private communications network connecting the US air traffic control system had triggered a system reboot, resulting in a crash and communications outage.

The FBI did not believe the stoppage was caused by a cyberattack or criminal activity, according to a Bloomberg report. Investigators were examining whether a software update could have triggered the outage.

Homeland Security Secretary Markwayne Mullin said there was no indication that the incident was a deliberate attack or a threat to the US.

How were international flights affected?

The European aviation agency Eurocontrol suspended all US-bound departures from its 42 member states at the FAA's request, Reuters reported. The suspension was scheduled to run from 5 pm Eastern Time on Friday until midnight.

Mexico's federal aviation agency also grounded scheduled flights departing Mexican airports for the US.

Air India warned that the nationwide ground stop could have consequential effects on its flights to and from the US. The airline advised passengers to check their flight status before travelling to the airport.

The disruption also affected air cargo. Since the FAA's order applied to departing flights, cargo operations relying on air transport faced delays. FedEx said it was monitoring the situation and was prepared to activate contingency plans to minimise service disruptions.

Is this the first time the US has grounded all flights nationwide?

The latest incident was the first nationwide ground stop since January 2023, when a malfunction in a key FAA computer system disrupted flight operations across the country.

Before that, the last comparable nationwide grounding occurred following the September 11, 2001, terrorist attacks.