NOTAMs — What They Are & How to Read Them

Alexander Leslie

Mar 4·10 min read

Reading a notice to airmen (NOTAM) is a daunting task.

Decoding one — a feat of strength.

Even online translation tools — or apps like ForeFlight — are geared towards a target audience of pilots, air traffic controllers, and experienced aviation enthusiasts who have the FAA’s official “NOTAM Contractions” spreadsheet memorized by heart. They certainly aren’t for the average OSINT enthusiast reading an ADS-B radar.

No matter how bewildering, baffling, or downright obtuse NOTAMs might seem — they are indispensable for understanding weather patterns, airspace and airport conditions, flight paths over conflict zones, re-routes, no-fly zones, when and where missile tests and military exercises will occur, and situations on the ground (i.e. natural disasters) that require aircraft notification.

This guide will hopefully give you enough information to be able to decode NOTAMs with a relative degree of proficiency, while understanding their purposes and why they’re relevant for monitoring breaking news.

Notices to airmen (NOTAMs) are one of the ways that an ICAO member state’s aviation authority — like the FAA in the United States — alerts aircraft about potential hazards en route to their destination.

Although the FAA’s NOTAMs are not fully ICAO compliant, they follow much of the same formatting as the ICAO standard.

A NOTAM can serve a variety of purposes that range drastically in severity. A NOTAM can alert aircraft about a natural disaster, like volcanic ash (ASHTAM) which can obscure a pilot’s field of vision or an earthquake on the ground which damages the runway. NOTAMs could also signal a surprise visit from a foreign dignitary which forces an aircraft to re-route.

Or maybe, a North Korean missile test into the Sea of Japan?

However, the vast majority of NOTAMs alert pilots about daily, mundane occurrences that are of no use to OSINT enthusiasts. Like a flock of seagulls migrating to South Carolina for the winter (also known as BIRDTAM).

Or a warning not to fall asleep in the cockpit and crash into the turbines of a new wind farm:

Here are some of the reasons a NOTAM might be issued:

• Inoperable lighting on tall obstructions that are not visible at night.
• Airspace restrictions as the result of military exercises.
• Emergency flights from the Department of Defense, law enforcement, or intelligence community which conflict with commercial flight paths.
• Radio dead zones.
• No-fly zones.
• Natural disasters and their emergency response.
• Temporary construction projects.
• Closed runways.
• Etc.

Really, the potential use for a NOTAM is endless. They could signal *any* development in “establishment, condition, or change of any facility, service, procedure, or hazard in the National Airspace System (NAS)” — according to the FAA.

In the United States, we distinguish between all of these potential uses by using simplified categories with corresponding channels of communication. Although there are various subcategories and unofficial NOTAM classifications — not to mention significant differences between domestic and international NOTAMs, the latter of which are ICAO compliant — these are some of the broader ones as defined by the FAA:

NOTAM(D): “Distant” NOTAM — not “domestic.” These NOTAMs are disseminated beyond the local FSS and ATC — signaling an announcement for every facility part of the National Airspace System (NAS). They can be freely accessed on the FAA’s database. They include basic updates about facility conditions, including taxiway closures, apron closures, construction, etc.

(U)NOTAM: “Unverified” NOTAM. Considered NOTAM(D). These are unofficial NOTAMs that are sourced from places other than airport management. These are typically not made public.

(O)NOTAM: “Other information.” Also considered NOTAM(D), but verified. NOTAMs that do not comply with FAA or ICAO formatting standards, but contain useful information for pilots specific to a local facility.

Pointer: A NOTAM that literally “points” to another NOTAM. It is a supplementary NOTAM used by FSS/АTC to highlight important information as a reminder of potential hazards or changes in flight conditions.

FDC: NOTAMs issued by the National Flight Data Center (FDC). These are regulatory in nature and must be complied with. They typically signal safety hazards or emergencies. Airspace closures, reroutes, temporary flight restrictions (TFRs), etc. are communicated by the FDC.

SAA: “Special Activity Airspace” NOTAM. These are typically published when an airspace is open and active off-schedule.

NOTAM(L): Non-critical and non-safety related NOTAMs targeted specifically at military personnel. These NOTAMs are communicated via telephone or radio equipment and typically never made public — unless necessary.

This list is not exhaustive. There are many, many more classifications of NOTAMs. For the sake of your sanity — don’t try to memorize them all at once. It’s not worth it, especially when there are tips, tricks, resources, and software to help decode these announcements.

NOTAMs could also be considered (historically) as Class I or Class II. Class I NOTAMs are distributed through regular telecommunications, whereas Class II *were* published every 28 days in the Notice to Airmen Publication (NTAP). It was announced in May 2020 that the NTAP was to be decommissioned later that year. As of the NOTAM Modernization Effort — there is now little practical distinction between Class I and II NOTAMs. But, it is still important to mention this distinction because it *will* show up in archives if you’re conducting research about a specific event.

Now that you generally know what purposes a NOTAM serves, we can begin the process of reading them. Understanding these announcements could potentially help you infer things about the status of any given airspace — in any country — while monitoring what’s happening on the ground and making judgements about potential developments.

First off, where can you get NOTAMs?

If you’re in the United States, it’s pretty simple.

The two major sources for finding NOTAMs online are the FAA Federal NOTAM System (FNS) and the Department of Defense, Defense Internet NOTAM Service (DINS).

For international NOTAMs which are ICAO compliant, a full database can be found on the ICAO’s website here.

Here are what they look like:

If you’re looking specifically for Temporary Flight Restrictions (TFRs), there is a separate database for that. If you prefer a graphic representation of TFRs, check out SkyVector.

Now that we’re on one of the databases, we can check out our first NOTAM! Let’s use the FAA FNS NOTAM Search to get some examples:

Here we have an active NOTAM for Ronald Reagan Washington National Airport (KDCA) in Arlington, Virginia. It was issued at 2/18/2020 1653 (4:53pm) UTC (11:53am EST) and its end date — 9/30/2022 — is a placeholder and signals that its ongoing.

NOTAMs will always be in UTC.

Let’s examine the NOTAM keyword-by-keyword:

Almost all NOTAMs will begin with what is called an “accountable” airport — the facility that the NOTAM applies to. They will also always begin with an exclamation point (!). We know that this is a NOTAM(D), as opposed to an FDC NOTAM, because an FDC NOTAM will always begin !FDC.

The accountable airport here is !DCA — Reagan-Washington National.

The number — 02/248 — tell us when the NOTAM was issued.

The first number, 02, signals that the NOTAM was issued in February. Since we know from the NOTAM information that it was issued 2/18/2020 1653, we know that this adds up.

The second number, 248, is the NOTAM # for that month. This means that this was the 248th NOTAM issued in February 2020 for DCA.

This number combination helps us easily search for this NOTAM again in the database without having to look through the general DCA repository.

The next segment of information is pretty self-explanatory, but should be pointed out:

This is the “affected” area of the NOTAM. It may seem redundant, but it is important to distinguish between airports if there are multiple in the same area. Keep in mind that Washington, D.C. also houses Dulles International, Joint Base Andrews, and a variety of other facilities, helipads, and government installations nearby. This means that — although these facilities are near the affected area — DCA is the facility primarily affected by this NOTAM.

The next piece of information is critical:

This tells you what type of NOTAM this is. It is an Obstruction.

There are twelve major abbreviations you should know if you plan on reading NOTAMs:

(1) AD: Aerodrome

(2) AIRSPACE: Airspace

(3) APRON: Apron/Ramp

(4) COM: Communications

(5) NAV: NAVAID

(6) OBST: Obstruction

(7) OPD: Obstacle Departure Procedure

(8) RWY: Runway

(9) SID: Standard Instrument Departure

(10) STAR: Standard Terminal Arrival

(11) SVC: Services

(12) TWY: Taxiway

Okay, so what kind of obstruction are we dealing with? Let’s find out:

I know it looks complicated, but it isn’t that difficult once you get the hang of it. Stick with me here.

The obstruction is a CRANE. LGT indicates “light(s)” or “lighting” — that there is a light outage reported. More information on these NOTAMs can be found here. This is important for VFR pilots.

A full set of abbreviations for NOTAMs can be found here.

ASN refers to the Aeronautical Study Number issued by the FAA’s Obstruction Evaluation Group (OEG).

385529N0771242W is the coordinates of the obstruction — 385529N & 0771242W.

38° 55.29' N & 77° 12.42' W.

In practical terms, it is 9.1 nautical miles (NM) west-north-west of DCA.

Here is the exact location of the obstruction on Google Maps:

We can verify this location further, mapping out the walking distance from the obstruction to DCA and comparing it (with some leeway) to the nautical mile distance:

The coordinates are about 10.3 miles away from DCA, 13.4 miles walking — which lines up almost exactly with the NOTAM’s 9.1 NM (10.1 miles) distance.

The obstruction is 891 ft. tall, or, 606 ft. Above Ground Level (AGL).

U/S means “unserviceable.”

Now, the final piece of information:

This is the WEF — “when in effect times” or “time in effect.”

20 (2020) 02 (February) 18 (18th) 1653 (4:53pm UTC / 11:53am EST) to 22 (2022) 09 (September) 30 (30th) 2359 (11:59pm UTC / 6:59pm EST).

Wow, that’s a lot of information right?

Let’s look at that NOTAM again:

Now that we’ve gone through it, line-by-line, we can translate this NOTAM into plain English:

“There is an unlit crane in Falls Church, Virginia, about 10.1 miles northwest of Ronald Reagan Washington National Airport. It is about 891 ft. tall. It is an active obstruction, it is known to the FAA, and the notice was issued on February 18th, 2020, at 11:53am EST.”

Much simpler and more informative, right?

Let’s try another quick example, using the same resources and methods from the first:

This NOTAM is for Chicago-Midway International Airport (KMDW).

Using the same exact methods of reading, with the same resources and links I provided earlier, we can translate this NOTAM into simple English:

“The painted surface for the holding position signs on Taxiway Y6 at Chicago-Midway International Airport is faded. Taxiway Y6 is at the end of Runway 22L. This warning was issued on February 26th, 2021 at 5:28 CT and is active.”

Easier? Trust me, you will get the hang of it the more you practice. These NOTAMs are relatively simple, straightforward, and do not signify emergencies. Those urgent NOTAMs surely exist, but they are much more complicated and time-sensitive.

The more you practice finding NOTAMs, decoding them, and inferring information from them — the easier it will get. It will require a lot of time and memorization, but it is worth it!

Continue following along with this blog series for posts that will consistently build on your skills!

Further resources and reading:

Alexander Leslie is a foreign policy analyst, freelance journalist, and has an M.A. in Eurasian, Russian, & East European Studies from Georgetown University. His interests include U.S.-Georgia relations, energy politics, and studies in counterterrorism policy.

Contact: aejleslie@gmail.com

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