NOTAM
A Notice to Airmen or Notice to Air Missions (US wording) (NOTAM), is a notice filed with an aviation authority to alert aircraft pilots of potential hazards along a flight route or at a location that could affect the flight. NOTAMs are unclassified notices or advisories distributed by means of telecommunication that contain information concerning the establishment, conditions or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel and systems concerned with flight operations. NOTAMs are created and transmitted by government agencies and airport operators under guidelines specified by Annex  15: Aeronautical Information Services of the Convention on International Civil Aviation (CICA). The acronym "NOTAM" came into common use following the ratification of the CICA, which came into effect on 4 April 1947. Notices to airmen were normally published in a regular publication by each country's air authorities (e.g., in "Flight International" magazine in the UK). A number of developments and amendments to the CICA have resulted in the more automated system available today. 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 a means of disseminating relevant NOTAMs to pilots. Usage. NOTAMs are issued (and reported) for a number of reasons, such as: Aviation authorities typically exchange NOTAMs over Aeronautical Fixed Telecommunication Network (AFTN) circuits. Software is available to allow pilots to identify NOTAMs near their intended route or at the intended destination. Some complain that the volume and increasing triviality of NOTAMs has reduced their usefulness. In the U.S. Air Force information technology enterprise, C4 NOTAMs (command, control, communications, and computer notices to airmen) are notices of new or updated Air Force Network Operating Instructions (AFNOIs). Often, these notices  serve to direct Air Force computer administrators to install security updates or change the configuration of computer systems. Criticism. In July 2017, Air Canada Flight 759 nearly crashed into four other airliners as it attempted to land on a San Francisco taxiway misidentified as a runway: the next runway was closed but the information was buried in the NOTAM. In September 2018, the National Transportation Safety Board stated NOTAMs were unintelligible and ignored, and recommended a more effective information presentation for better relevance. Flight planning applications for electronic flight bag can help decipher and better organize NOTAMs. Format. The following  describes ICAO NOTAMs. NOTAMs are published using all upper case letters which are claimed by some to make NOTAMs difficult to read. Note that some countries such as the United States may diverge from the following ICAO standards. Example. This is a typical NOTAM for London Heathrow airport: This decodes into the following: U.S. domestic NOTAMs. In the United States, NOTAMs are classified by the FAA into five categories: