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Another aspect that requires the attention of Digital NOTAM receivers is the risk of duplicate information, in particular for data situated in the vicinity of two or more areas of responsibility. This duplication already exists today in the form of different NOTAM messages issued by different States for the same facility or situation. With Digital NOTAMs, this risk to happen as well because of potential difficulties in coordinating the data publication between neighboring States, also taking into consideration the need for rapid data dissemination. With Digital NOTAMs, the risk should be reduced at least when it concerns updates to existing facilities, as the TEMPDELTA is expected to be issued by the same authority who has issued the BASELINE data. However, for situations when a new temporary item is announced (such as a temporary obstacle in the vicinity of the boundary), there is still a risk of lack of coordination. This may result in duplicate data being issued. Therefore, Digital NOTAM recipients should foresee appropriate actions for dealing with both potentially duplicate PERMDELTA and BASELINE data.

Discrepancies between digital data and NOTAM text


  • explain that this is a general issue, it may concern all AIS products
  • Annex 15 says that it is the obligation of AIS to ensure consistency
  • it is an error, it is not possible to indicate in advance which of the products (the digital or the pre-formatted takes precedence)