The blue points on the Flightradar24 map indicate airports that have regular, daily scheduled passenger flights within areas where Flightradar24 typically has coverage.
By clicking on a blue airport marker, you can access:
Arrival and departure boards for the airport.
Information on aircraft currently on the ground.
Detailed weather conditions at the airport.
You can also adjust the visibility of these airport markers in the map settings to customize your viewing experience.