Wednesday, January 11 was one of the most chaotic days in recent American aviation history. Thousands of flights were grounded for hours or canceled altogether due to a rather obscure system used by the FAA.

Why is the system so important? 

In the United States, the Federal Aviation Administration's NOTAM system, or "Notices to Air Missions" is of paramount importance in the aviation industry for the protection of aircraft from incidents and accidents. This system gives pilots the information they need regarding potential hazards in all phases of flight. A NOTAM can include information regarding flight conditions, obstacles such as cranes, and unserviceable instrument approaches, among several other pertinent information. It is crucial that this system is constantly operational. Without it, pilots may no longer fly with 100% certainty of safety and security, something paramount to an industry heavily based on mass transportation across vast distances.

The Trouble Begins 

A corrupt file was mistakenly downloaded onto the NOTAM system on Tuesday afternoon. This file caused the system to malfunction and soon fail at around 20:30 UTC (15:30 EST).  The FAA thought the problem was resolved, but as it turns out, the system's backup was also fed bad data. On Wednesday morning, when it became apparent that the NOTAM system was still not operating as it should have, the decision was made to shut down, reset, and test the system before it was officially back online. At 12:15 UTC (07:15 EST), the FAA issued an official nationwide ground stop for domestic departures, making it the first since 9/11. The ground stop was lifted just under two hours later at 09:00 EST (14:00 UTC).

What is a Ground Stop? 

A ground stop is a way to manage traffic during an emergency or when another issue requires all operations to cease for reasons of safety. This is where all aircraft of either an airline at a specific airport (if the airline issues the ground stop), or where all of the airports in a country are forced to keep all aircraft on the ground if they haven't yet departed. When a ground stop is issued, planes already in the air may continue to their destinations but are advised to exercise extreme caution.

Cascade Effect 

Despite the nationwide ground stop lasting only approximately 2 hours (ground stops had also been issued by airlines, which caused the delay times to drastically vary depending on the company), 1,300 flights were canceled, with an additional 9,500 flights taking off with some amount of delay with the average delay being three to five hours long. During this time, international flights and domestic ones already in the air were allowed to continue flying and land at their destination airports. This led to mass congestion across the United States, further adding to the chaos.

How did the United States government respond?

Throughout the evolving situation of the NOTAMs outage, the United States Secretary of Transportation Pete Buttigieg was actively releasing updates regarding the incident, as well as briefing the president about the outage. Many U.S. lawmakers are pushing the FAA to implement a more robust NOTAM system while dubbing the federal agency's current system "unacceptable".

Strange Coincidence 

At the same time the U.S. NOTAM system went down, so did that of Canada. Unlike the United States, no nationwide ground stop was issued as the magnitude of the situation was not as severe and widespread. A statement regarding the rather brief crash of the Canadian NOTAM system was released by Nav Canada stating "...[Canada's] NOTAM entry system is currently experiencing an outage affecting newly issued NOTAM's... We are not currently experiencing any delays related to this outage...".

Canadian traffic entering the United States was also heavily affected by the U.S. NOTAM outage. By the end of the day, however, no delays of cross-border traffic were noted.

Meanwhile, on Thursday, the ripple effects were still being felt from the outage. By Friday morning, January 13, all air traffic in the United States and Canada had returned to its normal flow.