The Evolution of NOTAMs

The concept of notifying pilots of changes or hazards impacting their flight dates back to the early days of aviation, when pilots relied on ad hoc bulletins or notices distributed by national aviation authorities. Over time, as air traffic grew and operations became more complex, the need for a formal notification mechanism became apparent.

With the creation of ICAO in 1947, a more standardized global framework for aviation information emerged. The acronym NOTAM (Notice to Airmen or Notice to Air Mission) entered common usage alongside a standardized method to create the relevant information.

At first, NOTAMs were relatively simple: they supplemented regular aeronautical information publications (AIP) or charts with timely alerts about changes, hazards, or temporary conditions (runway closures, obstacles, etc.). As systems evolved, the content of the NOTAM has expanded, and the method of transmission shifted to the use of the AFTN.

What NOTAMs Cover

Today, a NOTAM is a formal notice containing information about the establishment, condition, or change in any aeronautical facility, service, procedure, or hazard, the timely knowledge of which is essential to flight operations. Owing to loose definitions, liability concerns, and an overall global reach of aviation, NOTAM content now encompasses far more information than originally anticipated ~80 years ago.

READ ALSO: Understanding NOTAMs in Aviation

Understanding NOTAM Structure and Types

Under the guidance of ICAO Annex 15, the structure of a NOTAM is well-defined. The benefits of this structure are often lost owing to free-text or inconsistent application of the NOTAM from individual NOTAM Offices (NOFs).

Some common NOTAM categories are:

• Aerodrome / runway NOTAMs: closures, lighting outages, pavement conditions, snow/ice, taxiway availability.
• Navigational aid (NAVAID) NOTAMs: malfunctioning VORs, ILS, GPS outages, etc.
• Airspace / restriction NOTAMs: temporary flight restrictions, military exercise zones, special use airspace, drone/UAS restricted areas.
• Obstacle / crane notices (OBST): tall structures or cranes near active flight paths.
• Hazard or event notices: bird concentrations, snow/ice conditions (SNOWTAM), volcanic ash (ASHTAM), rocket launches, parachuting, laser activity.
• Procedure / chart changes: changes in instrument approach or departure procedures, missed approach fixes.
• Service communications: failures in communications links, ATC services, lighting, radar, etc.
• Regulatory / security / administrative: VIP movement, special events, temporary no‑fly zones.

https://nats-uk.ead-it.com/cms-nats/export/sites/default/en/NOTAM/NOTAM/NOTAM-Guidance-Material-Version-6.0-10_08_2023.pdf

A Growing Volume of Information

Various entities in aviation receive and database NOTAMs from NOFs globally. A survey conducted in 2020 revealed that there were 1.7 million new NOTAMs issued. Of this number, AIR SUPPORT personnel have determined that an average of 600 new NOTAMs each day are relevant for flight planning constraints.

https://ops.group/blog/the-notam-team/

Why the Number of NOTAMs Keeps Rising

Despite sophisticated charts, on‑board navigation systems, and predictive data used in modern aviation, NOTAMs are still required for the simple reason that no alternative has been developed that fulfils the role as a source for transmitting timely aeronautical changes. The industry has long identified the current NOTAM system as a safety hazard and liability, yet replacing NOTAMs with a new process has proven to be unattainable thus far. Numerous reasons can be attributed to the difficulty, including the below.

Non-Compliance To ICAO Guidance

According to ICAO Annex 15, NOTAMs are to be used for activities of a short duration and are to remain valid for no longer than 90 days. Any information still valid thereafter should be distributed via a formal publication: AIRAC AMDT, Supplement, or AIC. Even with this guidance, NOTAM databases contain NOTAMs that are 10+ years old. Because NOTAMs sometimes persist past their useful life, pilots face “clutter” that can obscure critical items.

Difficulty in Filtering

In aviation, where safety is paramount, it can be difficult to determine which NOTAMs are operationally relevant and which are marginal. To offset the sheer volume of NOTAMs, flight planning systems offer users the ability to reduce their NOTAM package through electronic filters. However, due to inconsistencies in NOTAM issuance – namely with the Q-Code, effective times, and keywords, more NOTAMs than necessary are presented to the flight crew. Conversely, aggressive filtering can lead to relevant NOTAMs being omitted.

Legacy Habits and Legal Liability

Following with the safety mentality, many NOTAM originators and NOFs take the position of ‘more information is better than less’, which results in issuing a NOTAM even for minor changes. This leads to policies that lack clear criteria and oversight, whereby NOTAMs for minor issues (e.g., small crane operations, low antennas, grass cutting) are being published, even if the operational impact is negligible.

Omitting a NOTAM that later leads to an incident may expose liability. Thus, there is an understandable resistance to removing “non‑critical” NOTAMs. Additionally, airspace users are subject to the regulations stipulated by their CAA, who can conduct ramp checks and audits of the flight crew’s documentation. Any NOTAM excluded from the NOTAM package that is deemed relevant by the Regulator could result in penalties being levied.

Technical & Data Architecture Constraints

Traditional NOTAM systems are often constrained by legacy architectures (e.g., plain text, limited fields, AFTN routing). These systems lack complicated functionalities or filtering capabilities, making it hard to suppress irrelevant NOTAMs automatically. The shift to new NOTAM systems is complex and expensive. In an environment where the digital NOTAM is not widely used, the reluctance of ANSPs to invest in new systems is understandable.

https://store.icao.int/en/annex-15-aeronautical-information-services

Modernization Efforts and the Digital NOTAM

Despite technical constraints, the move to digital NOTAM is gaining traction globally. The AIXM-based digital format aims to make them machine‑friendly and more selectively filtered, but the underlying function is still essentially the same: a message containing timely changes to aeronautical information.

In the meantime, various organizations have launched initiatives with the focus on reducing the number of NOTAMs to be reviewed by the Dispatcher / Flight Crew. While valiant, these initiatives still do not address the core problem: too many NOTAMs are being issued.

https://ext.eurocontrol.int/aixm_confluence/display/ADTKIT/Overview?preview=/39880480/75989302/DigitalEventOverview.png

The Way Forward

NOTAMs remain a critical link in the chain of aviation safety, bridging the gap between static aeronautical data and real‑time operations. Their history stretches back decades, evolving from simple bulletins to the forthcoming digital format with content ranging from runway closures to airspace restrictions to navigational outages.

Yet the problem of too many NOTAMs is real: pilots often find themselves sorting through pages of NOTAMs to identify relevant content. Efforts to reduce that clutter run into challenges of judgment, organizational inertia, legacy systems, safety conservatism, and the need to coordinate across many stakeholders.

The path forward lies in modernization: adopting structured digital NOTAM formats, enhanced filtering and relevance scoring, better criteria for issuance and cancellation, and improved user interfaces. But even with better tools, the underlying requirement remains: how to deliver complete, timely safety-critical information while minimizing distraction and overload. While technologies evolve, the core concern surrounding the number of NOTAMs will remain an active concern in aviation for years to come.

How to Handle NOTAMs Today?

AIR SUPPORT has added NOTAM keyword highlighting in CrewBriefing (see the Help Centre article below) and alerts and warning messages in the OpsControl | NOTAM Watch module – enabling dispatchers and flight operations to manage NOTAMs more easily and with greater confidence. 

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