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What's behind the latest air travel chaos? Problems with the little-known NOTAM system

Hundreds of flights were delayed or cancelled across the U.S. early Wednesday, spotlighting the importance of a little-known, and critics say antiquated, computer system that generates pre-flight alerts for pilots and other aviation staff.

Pilots couldn't access latest data on airspace closures and route weather due to technical problems

Silhouettes of travellers with suitcases are seen in an airport in front of an airplane.
People pass through Salt Lake City International Airport on Wednesday. Thousands of travelers were stranded at U.S. airports due to an hours-long computer outage impacting the latest safety information provided to pilots. (Rick Bowmer/The Associated Press)

Hundreds of flights were delayed or cancelled across the U.S. early Wednesday, spotlighting the importance of a little-known, and critics say antiquated, computer system that generates pre-flight alerts for pilots and other aviation staff. 

The Notice to Air Missions (NOTAM) system provides pilots and flight crew with a host of key safety information. From weather conditions on route, to airspace closures and potential problems at airports, pilots need the latest data from the system in order to fly, said John Pottinger, president of Pottinger Aviation Safety, a Canadian consultancy firm. 

"It's a notice of everything you are going to need to know before you make a flight," he told CBC News on Wednesday of the NOTAM system, which is communicated to pilots digitally. "Are these systems reliable enough and secure enough? If it even goes down for an hour or two, you can see what happens."

More than 1,200 flights in the U.S. had been cancelled by 4 p.m. ET Wednesday, according to FlightAware, a tracking website. More than 8,700 flights were delayed following problems with the U.S. NOTAM system, which also resulted in a number of Canadian flights to and from the U.S. being disrupted Tuesday and Wednesday. 

The FAA reported that the NOTAM system failed around 3:30 p.m. ET Tuesday, meaning no new messages about up-to-date weather or airport conditions could be processed. The grounding of many flights in the U.S. was lifted around 9 a.m. ET on Wednesday. 

Problems with the NOTAM system in the U.S., and the ensuing flight cancellations, have raised questions about how it's designed and whether the underlying digital infrastructure used to communicate information to aviators is up to the job. 

WATCH | Aviation safety expert explains computer system problems: 

Aviation safety expert explains NOTAM system outages

11 months ago
Duration 7:36
Featured VideoJohn Pottinger, the president of Pottinger Aviation Safety, talks about what may have contributed to the computer outages in the United States and Canada that resulted in thousands of delays and hundreds of cancellations.

When was NOTAM created and how does it work? 

According to the U.S. Federal Aviation Administration (FAA), the NOTAM system was first established in 1947.

NOTAMs must be provided to the pilots of any plane, big or small, private or commercial, before takeoff, Pottinger said.

Decades ago, the latest information was communicated to flight crews in person before departure. The system then became telephone based, and pilots would receive a call with updates on conditions.

In the last three to four years, the NOTAM system was digitized following guidance from the UN's International Civil Aviation Organization (ICAO), Pottinger said, and most updates are sent online. 

These digital systems aren't as robust as they should be in many places including the U.S., the aviation consultant said, as evidenced by Wednesday's outage. 

"If they fail, that means you are going to have significant delays." 

The silhouette of a traveller is pictured in front of an airport board showing cancelled slights.
A traveller looks at a flight board with delays and cancellations at Ronald Reagan Washington National Airport in Arlington, Va., on Wednesday. Transportation officials are probing the cause of the computer problems which forced the cancellations of more than 1,400 flights. (Patrick Semansky/The Associated Press)

Airports and air traffic control regulators and organizations such as the FAA and NAV Canada, create the notices that are sent to the system.

An airport might include information such as updates about a closed runway or lighting problems, Pottinger said. Air traffic regulators provide information on issues like airspace closures or weather hazards en route. 

This information is made available to pilots, airline staff and others in the industry ahead of a flight.

What caused the problem? 

Officials with the FAA haven't said what specifically went wrong with the NOTAM system. But U.S. officials said they don't believe the outage was related to a cyberattack.

U.S. President Joe Biden said he has directed the Department of Transportation to investigate the outage.

Transportation Secretary Pete Buttigieg told CNN that there would be ripple effects from the morning's delays.

"Now we have to understand how this could have happened in the first place. Why the usual redundancies that would stop it from being that disruptive did not stop it from being disruptive this time." 

An airline takes off and passed an airtraffic control tower as it rises into the sky.
A Southwest Airlines passenger jet takes off from Chicago's Midway Airport as flight delays stemming from a computer outage at the Federal Aviation Administration brought departures to a standstill across the U.S earlier Wednesday. (Charles Rex Arbogast/The Associated Press)

Was Canada affected? 

NAV Canada, the organization responsible for air traffic control in this country, reported an outage for new updates to the NOTAM system for a couple of hours mid-morning Wednesday, but said the problem didn't cause any flight delays.

In Canada, pilots were still able to read NOTAMs, but there was an outage that meant new notices couldn't be entered into the system, NAV Canada said on social media. 

When new information couldn't be added to the platform, Pottinger believes Canadian air traffic control officials may have reverted back to phone calls to communicate the latest data to pilots.

NAV Canada said it did not believe the outage was related to the one in the U.S., but it said it was investigating.

What happens next? 

Problems with the NOTAM system did not put passenger safety at risk, Pottinger said, but the outage did cause major headaches for travellers and airlines. 

Some of the digital "background architecture" underpinning the NOTAM system "is pretty old in the U.S. and Canada," he said, noting that technology glitches likely contributed to the problem.

Travel industry officials called on the government to improve the system. 

"America's transportation network desperately needs significant upgrades," Geoff Freeman, president of the U.S. Travel Association, said in a statement. "We call on federal policymakers to modernize our vital air travel infrastructure."


  • An earlier version of this story referred to NAV Canada as a government body. In fact, NAV Canada is a privately run, not-for-profit corporation that owns and operates Canada's civil air navigation system.
    Jan 11, 2023 10:24 PM ET
  • An earlier version of this story also said the UN's International Civil Aviation Organization (ICAO) regulates the global system. In fact, it does not regulate the system, but promotes aviation safety by helping to define international operating standards.
    Jan 12, 2023 11:43 AM ET

With files from Reuters and The Associated Press