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Parser for NOTAM (Notice to Airmen) messages in Ruby.



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Add the following to the Gemfile or gems.rb of your Bundler powered Ruby project:

gem 'notam'

And then install the bundle:

bundle install --trust-policy MediumSecurity


raw_notam_text_message = <<~END
  W0902/22 NOTAMN
  Q) LSAS/QRRCA/V/BO/W/000/148/4624N00702E004
  A) LSAS PART 2 OF 3 B) 2204110900 C) 2205131400 EST
  D) APR 11 SR MINUS15-1900, 20-21 26-28 MAY 03-05 10-12 0530-2100, APR
  14 22 29 MAY 06 13 0530-1400, APR 19 25 MAY 02 09 0800-2100
  F) GND
  G) 14800FT AMSL
  CREATED: 11 Apr 2022 06:10:00

notam = NOTAM.parse(raw_notam_text_message)    # => Hash

The resulting hash for this example looks as follows:

  id: "W0902/22",
  id_series: "W",
  id_number: 902,
  id_year: 2022,
  new?: true,
  fir: "LSAS",
  subject_group: :airspace_restrictions,
  subject: :restricted_area,
  condition_group: :changes,
  condition: :activated,
  traffic: :vfr,
  purpose: [:operational_significance, :flight_operations],
  scope: [:navigation_warning],
  lower_limit: #<AIXM::Z 14800 ft QNH>,
  upper_limit: #<AIXM::Z 0 ft QFE>,
  center_point: #<AIXM::XY 46.40000000N 007.03333333E>,
  radius: #<AIXM::D 4.0 nm>,
  locations: ["LSAS"],
  part_index: 2,
  part_index_max: 3,
  effective_at: 2022-04-11 09:00:00 UTC,
  expiration_at: 2022-05-13 14:00:00 UTC,
  estimated_expiration?: false,
  no_expiration?: true,
  schedules: [
    #<NOTAM::Schedule actives: [2022-04-11], times: [sunrise-15min..19:00 UTC], inactives: []>,
    #<NOTAM::Schedule actives: [2022-04-20..2022-04-21, 2022-04-26..2022-04-28, 2022-05-03..2022-05-05, 2022-05-10..2022-05-12], times: [05:30 UTC..21:00 UTC], inactives: []>,
    #<NOTAM::Schedule actives: [2022-04-14, 2022-04-22, 2022-04-29, 2022-05-06, 2022-05-13], times: [05:30 UTC..14:00 UTC], inactives: []>,
    #<NOTAM::Schedule actives: [2022-04-19, 2022-04-25, 2022-05-02, 2022-05-09], times: [08:00 UTC..21:00 UTC], inactives: []>
  five_day_schedules: [
    #<NOTAM::Schedule actives: [2022-04-11], times: [04:35 UTC..19:00 UTC], inactives: []>,
    #<NOTAM::Schedule actives: [2022-04-14], times: [05:30 UTC..14:00 UTC], inactives: []>
  translated_content: "R-AREA LS-R7 HONGRIN ACTIVE DUE TO FRNG.",
  created: 2022-04-11 06:10:00 UTC,
  source: "LSSNYNYX"

A few highlights to note here:

  • Value classes of the AIXM gem are used to ease further processing.
  • Schedules can be pretty complex, therefore a simpler five_day_schedule is calculated for the day the NOTAM becomes effective and the four subsequent days. This short term schedule does not contain exceptions nor events such as sunrises anymore. Furthermore, you can calculate different custom sub-schedules using slice and resolve.
  • Content is processed to translated_content. As of now, known english contractions are expanded. Feel free to contribute non-english locale files read by the I18n gem.

Since NOTAM may contain a certain level of redundancy, the parser does some integrity checks, fixes the payload if possible and issues a warning.

You get a NOTAM::ParseError in case the raw NOTAM text message fails to be parsed. This error object features two notable methods:

  • item – the faulty item (if already available)
  • cause – the underlying error object (if any)

If you're sure the NOTAM is correct, please submit an issue or fix the bug and submit a pull request.

See the API documentation for more.

⚠️ Only NOTAM compatible with the ICAO annex 15 are supported for now. Most notably in the USA other NOTAM formats exist which cannot be parsed using this gem.

Anatomy of a NOTAM message

A NOTAM message consists of the following items in order:

  • Header: ID and type of NOTAM
  • Q item: Essential information such as purpose or center point and radius
  • A item: Affected locations
  • B item: When the NOTAM becomes effective
  • C item: When the NOTAM expires
  • D item: Activity schedules (optional)
  • E item: Free text description
  • F item: Upper limit (optional)
  • G item: Lower limit (optional)
  • Footer: Any number of lines with metadata such as CREATED and SOURCE

Furthermore, oversized NOTAM may be split into several partial messages which contain with PART n OF n and END PART n OF n markers. This is an unofficial extension and therefore the markers may be found in different places such as on the A item, on the E item or even somewhere in between.


Four letter FIR codes assigned by the ICAO follow some logic, albeit there exist exceptions and inconsistencies e.g. for historical reasons. Let's take an easy example:

┬ ┬ ─┬─
│ │  └─ subsection: MM => Marseille
│ └──── geopolitical unit: F => France
└────── global area: L => lower Europe

The informal use of only the first two letters often stands for a combination of all subsections contained therein. Example: LF is a combination of LFBB, LFEE, LFFF, LFMM and LFRR.

FIR codes ending with XX specify more than one subsection. Example: LFXX can be any combination of at least two subsections within LF. In NOTAM, this notation may be used on the Q item if (and only if) the affected subsections are listed on the A item.


The first letter of the NOTAM ID is identifying the series. The following example is part of series S:

S0054/02 NOTAMN

AIS are free to define series as they please, however, a few conventions have emerged:

  • Series A
    General rules, en-route navigation and communication facilities, airspace restrictions and activities taking place above FL 245 as well as information concerning major international aerodromes.
  • Series B
    Information on airspace restrictions, on activities taking place at or below FL 245 and on other international aerodromes at which IFR flights are permitted.
  • Series C
    Information on other international aerodromes at which only VFR flights are permitted.
  • Series D
    Information on national aerodromes
  • Series E
    Information on heliports
  • Series S (aka: SNOWTAM)
    Surface condition reports
  • Series T
    Reserved for NOTAM processing units in cases when basic operational information was not triggered by the issuing AIS.
  • Series V (aka: ASHTAM)
    Volcano ash condition reports

Special NOTAM


Checklist NOTAM are periodically issued lists of all currently effective NOTAM. They are used for cross checking and can usually be ignored for flight planning. Their Q item contain QKKKK which is decoded as condition: :checklist, here's an example:

Q) EDXX/QKKKK/K /K  /K /000/999/5123N01018E999


Trigger NOTAM are referring to another source of information such as AIP SUP (AIP supplement). Their Q item contain Q..TT which is decoded as condition: :trigger, here's an example:

Q) LFXX/QRTTT/IV/BO /W /000/035/4708N00029E010
        ^  ^^

Note: Trigger NOTAM are never published as series T.


For compatibility, schedule dates and times are expressed using the corresponding classes from the AIXM gem:

Raw and parsed NOTAM schedule times differ in how the "end of day" is encoded:

NOTAM Beginning of Day End of Day Remarks
Raw "0000" "2359" "2400" is considered illegal
Parsed 00:00 24:00 the Ruby way



You find the translations for each available language in lib/locales/. Additional translations are very welcome provided you have sufficient aeronautical background knowledge.

Please create a translation request issue, then duplicate the lib/locales/en.yml reference language file and translate it.

Tests and Fixtures

The test suite may run against live NOTAM depending on whether and how you set the SPEC_SCOPE environment variable:

export SPEC_SCOPE=none       # don't run against any NOTAM fixtures (default)
export SPEC_SCOPE=W0214/22   # run against given NOTAM fixture only
export SPEC_SCOPE=all        # run against all NOTAM fixtures
export SPEC_SCOPE=all-fast   # run against all NOTAM fixtures but exit on the first failure

The NOTAM fixtures are written to spec/fixtures, you can manage them using a Rake tasks:

rake --tasks fixtures


To install the development dependencies and then run the test suite:

bundle install
bundle exec rake    # run tests once
bundle exec guard   # run tests whenever files are modified

You're welcome to submit issues and contribute code by forking the project and submitting pull requests.


The gem is available as open source under the terms of the MIT License.