NOTAM is an acronym for "Notice to Airmen." According to the Federal Aviation Administration (FAA), a NOTAM contains information of essential importance to flight operations personnel that was not known far enough in advance to be distributed in another way. It notifies pilots, in particular, of the abnormal status of a component of the National Airspace System (NAS).
NOTAMs are issued by the FAA for many different reasons but primarily to inform pilots of changes involving airports, airways, and local procedures that may affect the safety of the crew or those on the ground.
There are many types of NOTAMs, including international, domestic, military, and civilian. They can be advisory in nature, or they can be mandatory directives. Both private and commercial pilots need to be aware of the different types of NOTAMs.
These NOTAMs are distributed both locally and to those in an area beyond that of the local flight service station (FSS) or air traffic controller (ATC). The letter "D" references the word "distant." They are divided into (U) NOTAMs and (O) NOTAMs. (U) NOTAMs are distributed by an unofficial source and are not verified by an airport manager. (O) NOTAMs are notices to pilots that don't meet the standards of a typical NOTAM but do contain important information.
NOTAM(L)s target only military personnel and are communicated locally over the radio or telephone. Military-only NOTAMs include safety concerns specific to military airfields and military operations not covered under the civilian NOTAM system. NOTAM(L)s previously issued for civilian pilots have been reclassified as NOTAM(D)s.
GPS NOTAMs are issued for an area experiencing either service problems or outages that are affecting the area's global positioning system.
Flight Data Center NOTAMs
Flight Data Center (FDC) NOTAMs are mandatory issuances and require compliance. These include safety hazards stemming from instrument approach procedures and airway changes. Temporary flight restrictions (TFRs) are one example of an FDC NOTAM. These NOTAMs are issued for necessary and immediate airspace closures, such as the airspace around the White House or the temporary closing of airspace around live events such as the Olympics.
Center Area NOTAMs
Center Area NOTAMs are FDC NOTAMs issued for a large area. They are initiated by the Air Route Traffic Control Center (ARTCC) and cover multiple airports. Airway restrictions, laser activity, and TFRs are three reasons for issuing a Center Area NOTAM.
Class I NOTAMs
These are normal NOTAMs that are issued via telecommunication, as opposed to being published.
Class II NOTAMs or Published NOTAMs
These are normal NOTAMs that are not issued via telecommunication. Instead, they are published in the Notices to Airmen Publication (NTAP), which is updated every 28 days.
International NOTAMs are distributed to more than one country and are published in International Civil Aviation Organization (ICAO) format and stored in the International section of the NTAP. International NOTAMs are not made available in regular flight service briefings and must be requested by a pilot.
These NOTAMs are issued in the United States and sometimes also in Canada and are produced in FAA format and not ICAO format.