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Flights across the US were grounded recently following an issue never experienced before. This was not due to weather or terrorism, but instead an outage of the NOTAM system. The situation was resolved after only a few hours, but it remains concerning that such a problem could cause such major disruption.

The NOTAM system

The collapse involved the NOTAM – or Notice to Air Missions – system. This used to be known as Notice to Airmen, but the name was changed in 2021. This is the global system that notifies pilots of any changes or hazards on a flight route or at an airport. This includes notifications about airspace changes or restrictions, airspace hazards, issues with runways or navigational aids, warnings of snow, birds, or ash. NOTAMs are shared internationally, with each country’s aviation authority distributing them.

Pilots will check NOTAMs appropriate for their journey as part of flight planning. This is now an integral part of the “electronic flight bag” with software management making this much easier. There was criticism in the past over the volume of NOTAMs in some cases and the possibility to overlook the more important ones.

Ground stop on January 11th

Early in the morning of January 11th 2023, the US FAA issued a nationwide ground stop order halting all flight departures. This followed the failure of the NOTAM system meaning that it was unable to sort and distribute notifications to pilots. With no other system in place to make this vital information accessible, a rare ground stop was the only safe solution.

This order was in place until 9am EST, affecting thousands of morning flights across the country. According to FlightAware, by mid-afternoon around 9,500 flights had been delayed (with 1,300 flights cancelled).

What happened to the NOTAM system?

The problem was simple – the NOTAM computer system used by the FAA failed. This in fact had stopped working late the previous evening. It was fully rebooted and restored early in the morning, but it still took some time to verify the data was once again being reported correctly. The backup system did not work either – likely as it is fed using the data.

Within 48 hours, the FAA released its initial insights into the outage. It blamed “personnel who failed to follow procedures” for the system collapse. The breakdown was linked to a damaged database file, which fed into both the main system and the backup.

Importantly, there has been no suggestion of any cyberattack or external involvement. The Canadian aviation authority, NAC Canada, also reported an outage the same day (but with much less disruption). This of course raised fears that there was a linked attack, but this appears to not be the case.

Details of exactly how the database was damaged, and how it fed into the main system so easily, have not been released. There is likely a failure of procedures though when (possibly) one person could introduce corrupted data, with no automated or simple process to recognise or halt this.

Thorough review expected

The exact cause, and the potential vulnerability of the system, will be thoroughly looked into. President Joe Biden has asked for a full investigation from the Department of Transportation. Speaking about the follow up required, Senator Maria Cantwell (the chair of the Senate Commerce Committee) explained:

“As the Committee prepares for FAA reauthorization legislation, we will be looking into what caused this outage and how redundancy plays a role in preventing future outages. The public needs a resilient air transportation system.”

The NOTAM system is now decades old, and at least six years away from any potential upgrade (according to reporting by CNN). It is possible that this outage will speed this up, but we will have to await any further reviews or announcement.

Final Thoughts

This was a serious problem, and it will be surprising to many that there is no quickly accessible and reliable backup or alternative for such an important source of information. On the other hand, however, this is the first time that such a failure has occurred. No doubt the following investigation will establish the cause in more detail and procedures will follow to minimise the likelihood or the impact of it happening again.


CNBC reporting and FlightAware data:



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