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This section contains the rules for the use of a mix of upper and lower case in the Digital NOTAM Specification. These rules need to be applied in particular when coding free text annotations. The rules are also applied in the Specification itself, when defining the text NOTAM generation scenarios (see the "Decoding Scenarios"). The high-level objective is to provide the event description formatted as a typical English language sentence, while also taking into consideration specifics of the aeronautical domain language, such as well-known abbreviations and acronyms. The major difference from the current NOTAM format is that the text is no longer written only in upper case, because it is not constrained by the AFS/AFTN character set limitations.


The Decoding part of the Event Specification is provided only for the English language. For other languages the item NOTAM generation templates and these rules will have to be adapted taking into consideration the specifics of that language.

These rules will apply to the text elements used in the templates for the NOTAM items E and also for the writing of the text in items D, F and G, with the purpose to provide a clear, meaningful and easy to read text for the user. The proposed rules for usage of upper/lower case for abbreviations/acronyms are aiming to be as simple as possible, however not losing the target to achieve normal text in the NOTAM. A very simplified rule could for instance have been to always have abbreviations/acronyms in upper case. However, such practice is not the best solution, since words in capital letters give the impression of shouting or being of special importance, which can create the wrong impression of the information. A degree of complexity is therefore inevitable in these rules. These rules are intended for application for both text that is automatically generated (from the AIXM coded fields) and for text used in AIXM annotations and other fields with text content (such as "instruction" properties). However, it is acknowledged that a human operator would have difficulties retaining all these rules and applying them strictly. Therefore, human operators are expected to keep in mind and apply the high-level principles for text sentence. 


General rules for usage of upper case characters:

  • The first letter in a sentence.
  • Each first letter of a name (such as 'Brussels South').
  • Location indicators.
  • Designators, such as five-letter ICAO designators for waypoints, navigation aid designators, route/SID/STAR designators, airspace designators, etc.

    AIXM 5.1 Limitation

    In AIXM 5.1(.1), all names are just in upper case. This is a limitation inherited from AIXM 4.5 where it was introduced exactly for facilitating the use of feature names in AFTN messages (such as NOTAM). This was raised as issue AIXM-236 to the AIXM Change Control Board and it is expected that this limitation will be eliminated in the next AIXM version (5.2). Workaround - an algorithm for converting Character3 data type into lower case is provided here.

General rules for usage of lower case characters:

  • Consecutive text after the first letter in a sentence.
  • Abbreviations, except those specifically mentioned to be written otherwise (see paragraph 1.5).
  • Spelled out abbreviations and acronyms, with the exception of the first letter for defined acronyms (for rules on spelled-out abbreviations and acronyms, see paragraph 1.5).

Special situations that require a mix of uppercase and lower case characters:

Rules for formatting acronyms and abbreviations:
Specific rules are defined for formatting abbreviations and acronyms in digital NOTAM text. These rules consider usage of upper and lower case together with rules for spelled-out text of abbreviations and acronyms, defining:

  • Abbreviations and acronyms that shall be spelled out, and usage of lower/upper case of the spelled-out text.
  • Abbreviations and acronyms that shall be kept and usage of lower/upper case of the abbreviated text.
  • Acronyms that shall be spelled out and with the first letter of each word in upper case.

The principle is that abbreviations/acronyms that are not commonly used, not included in ICAO Doc 8400 and/or may be subject to misunderstanding shall not be used, but instead be spelled out (e.g. use 'Area Chart' instead of "ARC").
The categories that fall under the defined rules are summarized in the table below.

Appendix A provides the detailed digital NOTAM format of the ICAO Doc 8400 abbreviations and acronyms following these rules.



Abbreviations that shall be spelled out and written in lower case.

ICAO Doc 8400 provides abbreviations for words that are already short, such as 'closed", available', 'active'. These words do not need to be abbreviated since the spelled out format does not significantly add to the length of the message. The spelled out text facilitates the understanding of the message.

  • short words
  • specified locations, e.g. above, beyond, before, under, abeam, between, below, behind, adjacent, across, centred, within.
  • cardinal points and their combinations, except when used after coordinates in lat/long.
  • colours
  • lighting types, except ALS (Approach Lighting System)
  • abbreviations not included in ICAO Doc 8400.

Abbreviations and acronyms that shall be kept and spelled in UPPER CASE.

Certain abbreviations and acronyms are so well known in the aeronautical domain that are regarded as true words, and shall therefore be kept and also be spelled in upper case.

  • air traffic services types
  • aerodrome, heliport
  • navigation and landing aid types
  • airspace types
  • months and days
  • com and surveillance systems
  • routes
  • codes for operating hours
  • level indicators (AMSL, GND, SFC)
  • certain aeronautical chart types
  • and more..

Abbreviations and acronyms that shall be kept and spelled in lower case.
In normal document text in the aeronautical domain, we are used to see certain abbreviations and acronyms spelled in lower case. The same principle applies also for the Digital NOTAM text.
"The most looked up abbreviations in our online dictionary are i.e. and e.g., probably because they are often confused for one another. You can use the e.g. and i.e. abbreviations both inside and outside the parenthesis."
´The purpose of this document is to provide templates for the Item E for some frequent issued NOTAM types, e.g. closed RWY, active restrictions etc."
"Closed for acft heavier than…"

  • certain often used acronyms/abbreviations

Acronyms that shall be spelled out and with the first letter of each word in upper case (also known as "title case")
Do not stress capital letters in normal fluent text, unless seen justified for certain terms, such as "Minimum Sector Altitude", "Temporary Reserved Area".
If the acronym is rarely used or un-known (e.g. "SD" for "standard deviation'), the spelled out words shall not capitalize the first letters of each words forming the acronym; instead, each word shall begin with lower case.

  • airspace, areas (Temporary Reserved Airspace)
  • altitudes types (e.g. Minimum Sector Altitude)
  • certain aeronautical chart types
  • Approach Lighting System

Examples of usage

Digital NOTAM text examples, in which the rules stated above are applied:

  • ILS/DME RWY 19 unserviceable.
  • RWY 01 closed.
  • Temporary Reserved Airspace ESTS310 activated.
  • THR RWY 19 displaced 400 m. Declared distances changed: TORA 2450 m, TODA 2450 m, ASDA 2450 m, LDA 2050 m.
  • Trigger NOTAM – perm AIRAC AMDT 02/14 wef 20 FEB 2014: new ATS route M123 established.
  • VOR DKB resumed normal operations.
  • Danger Area HED9 activated.
  • ATS operating hours changed as follows: 01 03 05 1000-1600 02 04 06-31 0800-2200.
  • EGNOS not available for LPV.
  • AWY G5 closed between WIL and FRI.
  • RNAV route N850 closed between GERSA and ODINA.
  • Temporary Restricted Area Narnia established.
  • Crane position 500545N 0141556E erected 190 m south of RWY 13/31 axis, 1300 m behind THR RWY 31, elev 390.3 m hgt 20.7 m AGL.
  • ILS RWY 25R unserviceable.
  • TWY A east of RWY 10/28 closed.
  • Minimum Sector Altitude southwest sector raised to 1700 ft AMSL.
  • Danger Area (EGD0421-10) established as follows: circle with radius 3 NM centered on 5306N 00400W. Between SFC and 500ft AMSL.
  • Aerobatics will take place within: circle with radius 2 NM centered on 4952N 00737E. Located at Pferdsfeld, 10 NM east Kirn VOR KIR. VMC activity.
  • THR RWY 35 displaced 1100 m. Declared distances changed:
    RWY 36 TORA 3200 TODA 3200 ASDA 3200 LDA 2100
    RWY 18 TORA 3200 TODA 2100 ASDA 3200 LDA 3200
  • Obstacle lights – Arge Hochhaus Neue Donau Wagramerstrasse 4 unserviseable. Position 481351N 0162456E, elev 168 m/155 ft, max hgt above GND 150 m/492 ft.
  • Information incorporated in AIP AMDT 4/17 wef 14 APR 2017.
  • RWY 08/26 extension AIRAC AIP AMDT 10/08 part AD: EGNX 2-12 RWY08 read 1850 m instead of 1805 m.
  • Crane position 500545N 0151456E erected 190 m south of RWY 13/31 axis, 1300 m behind THR RWY 31, max elev 390.3 m, max hgt 20.7 m AGL.
  • TWY A east of RWY 10/28 closed.
  • ILS GP RWY 11 unserviceable.
  • RWY 03 Approach Lighting System medium and high intensity unserviceable
  • RWY 05/23 closed, except for EMERG flights, HOSP flights.
  • TWY 1 segment closed from TWY 6 to TWY 2. TWY 2, 3, 4, 5, 6 closed.
  • RWY 34 THR displaced 1080 ft. Except 30 min PPR TWR 121.875 daily 1200-2230.
  • CTR Donlon activated as follows:
    APR 23 0445 – 1800
    APR 28 0615 - 2030

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