These icons do appear to be caused by the Navigraph data and there has been some existing discussion. You may wish to check the following topics for more:
From Navigraph forums: MSFS World map - All airports marked as 3rd party - Navigraph Forums
These icons do appear to be caused by the Navigraph data and there has been some existing discussion. You may wish to check the following topics for more:
From Navigraph forums: MSFS World map - All airports marked as 3rd party - Navigraph Forums