A notice identified either as a NOTAM or Airmen Advisory containing infromation concerning the establishment, condition, or change in any component of, or hazard in, the National Airspace System, the timely knowledge of which is essencial to personnel concerned with flight operations. (1) NOTAM. A Notice to Airmen in message form requiring expeditions and wide dissemination by telecommunications means. (2) Airmen Advisory. A Notice to Airmen normally only given local dissemination, during preflight or in-flight briefing, or otherwise during contact with the pilots.