On the Flightradar24 website, larger airports are reflected by larger airport pins on the map while smaller airports have smaller pins. The size of the airport is determined by the number of take offs and landings. It's possible to turn off the airport pins or add a label. This can be done from Settings > Map > Airport pins and labels. The label includes the airport name and IATA/ICAO codes of the airport. In the apps currently, the airport pin sizes are the same whatever the airport size.
