Flight notes is a facility provided by Celebris. It is not related with sita messages.
In Celebris, It is possible to enter a note about a flight with the idea of internal messaging about a flight. When a message is created about a flight, it will be seen in the landings main screen too (see main landings screen).
In Celebris, a flight and a landed are separate entities. A landed consists of two flights: one arrival and one departure. It is possible that the arrival flight of a landed is the departure flight of another landed in another airport. Celebris cleverly assigns the previously created flight to a landed if the flight is generated using one of the two provided utilities: flight copy and flight plan. Therefore, it is possible that a message about a flight entered by the staff at the departing airport is seen as a message to a flight in the arrival airport.
Flight messages are not to be confused with landing related messages.