ICAO text NOTAM are transmitted over AFTN and have to comply with certain technical limitations of this network. One such limitation concerns the maximum length of a message - 1800 characters. A message longer than 1800 characters needs to split into a “multi-part” message, but this split also is limited to 26 times. However, a NOTAM that would need more than 26 x 1800 characters is unlikely to exist, as it would seriously break the ICAO rules for information publication by NOTAMs.

NOTAM messages that would require to be split into up to 5-6 parts for AFTN transmission are likely to be encountered from time to time. From the point of view of the Event Schema, they should be treated as a single NOTAM messages and stored as one (consolidated) NOTAM object instance.

The split will occur only for AFTN transmission purpose. In addition, it is recommended that a series of warnings are displayed by a Digital NOTAM encoding tool to the operator, as follows: