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NOTAM or NoTAM is the quasi-acronym for a "Notice To Airmen". NOTAMs are created and transmitted by government agencies under guidelines specified by Annex 15: Aeronautical Information Services of the Convention on International Civil Aviation. A NOTAM is filed with an aviation authority to alert aircraft pilots of any hazards en route or at a specific location. The authority in turn provides means of disseminating relevant NOTAMs to pilots.

NOTAMs are issued (and reported) for a number of reasons, such as:

• hazards such as air-shows, parachute jumps, kite flying, rocket launches, etc.
• flights by important people such as heads of state (sometimes referred to as Temporary Flight Restrictions, TFRs)
• closed runways
• inoperable radio navigational aids
• military exercises with resulting airspace restrictions
• inoperable lights on tall obstructions
• temporary erection of obstacles near airfields (e.g. cranes)
• passage of flocks of birds through airspace (a NOTAM in this category is known as a BIRDTAM)
• notifications of runway/taxiway/apron status with respect to snow, ice and standing water (a SNOWTAM)
• notification of an operationally significant change in volcanic ash or other dust contamination (an ASHTAM)
• software code risk announcements with associated patches to reduce specific vulnerabilities

Aviation authorities typically exchange NOTAMs over AFTN circuits.

Software is available to allow pilots to identify NOTAMs near their intended route or at the intended destination.

When computer systems for the air force are updated the software updates are usually referred to as NOTAMs

Format

The following describes ICAO NOTAMs, which may be different to US Domestic NOTAMs. Additionally, NOTAMs are poorly controlled and not all NOTAMs are issued using the required standards:

The first line contains NOTAM identification (series, sequence number and year of issue), the type of operation (NEW, REPLACE, CANCEL), as well as a reference to a previously-issued NOTAM (for NOTAMR and NOTAMC only).

The 'Q' line holds (basic-remove) information about who the NOTAM affects along with a basic NOTAM description. This line can be encoded/decoded from tables defined by ICAO.

The 'A' line is the ICAO code of the affected aerodrome or FIR for the NOTAM. The area of influence of the NOTAM can be several hundreds of kilometres away from the originating aerodrome.

The 'B' line contains the start time and date, the 'C' line the finish time and date of the NOTAM. The date is in a USA date format of YY/MM/DD and the times are given in Universal Co-ordinated Time; also known as GMT or Zulu time.

Sometimes a 'D' line may be present. This gives a miscellaneous diurnal time for the NOTAM if the hours of effect are less than 24 hours a day. E.g. parachute dropping exercises tend to occur for short periods of a few hours during the day, but may be repeated over many days.

The 'E' line is the full NOTAM description. It is in English but heavily abbreviated. These abbreviations can be encoded/decoded by tables defined by ICAO.

When present, 'F' and 'G' lines detail the height restrictions of the NOTAM. Typically SFC means surface height or ground level and UNL is unlimited height. Other heights are given in feet or flight level or a combination of the two.