7. A NOTAM notification computer system, comprising: a NOTAM notification processor; a memory communicatively coupled to the NOTAM notification processor; and a NOTAM notification application (i) which executes in the NOTAM notification processor and (ii) which, when executed by the NOTAM notification processor, causes the NOTAM notification computer system to provide relevant NOTAMs to a crew of an aircraft according to a target phase of flight by receiving a plurality of NOTAMs, determining a target phase of flight associated with the aircraft, retrieving relevance rules, the relevance rules comprising a relevance code for each of a plurality of NOTAM subject codes for each of a plurality of phases of flight, determining a relevance for each of the plurality of NOTAMs according to the relevance rules and target phase of flight, and providing a notification of one or more NOTAMs according to the relevance for the target phase of flight; wherein each relevance code comprises the relevance of the NOTAM subject code to a plurality of flight segments of a planned flight route such that determining the relevance for each of the plurality of NOTAMs according to the plurality of relevance rules and the target phase of flight comprises retrieving the relevance code corresponding to the target phase of flight and determining the relevance for each of the plurality of NOTAMs according to the corresponding relevance code, and wherein providing the notification of one or more NOTAMs according to the relevance for the target phase of flight comprises determining one or more types of notifications to provide according to each relevance code and providing the one or more types of notifications, and wherein the relevance code further comprises a multi-letter code including a plurality of letters, each of the letters being associated with one or more flight segments of the planned flight route, and each of the letters comprising an indication of relevance of the NOTAM subject code to the corresponding flight segment of the planned flight route for the target phase of flight.
8. The NOTAM notification computer system of claim 7 , wherein the relevance code comprises a four-letter code such that a first letter is associated with a departure airport or departure segment of flight, a second letter is associated with an alternative en route airport or en route segment of flight, a third letter is associated with an alternative destination airport, and a fourth letter is associated with a destination airport or arrival segment of flight.