The radius of the surface area of a class B airspace (for the busiest airports) might only be about 6 miles. http://vfrmap.com/?type=vfrc&lat=42.363&lon=-71.00

The radius of the surface area of a class B airspace (for the busiest airports) might only be about 6 miles. http://vfrmap.com/?type=vfrc&lat=42.363&lon=-71.006&zoom=10&api_key=763xxE1MJHyhr48DlAP2qQ http://vfrmap.com/?type=vfrc&lat=42.363&lon=-71.006&zoom=10&... Look for the blue SFC (surface) with a line over it designation around the area for the airport with the multiple concentric blue rings. Those will be class B airports. Typically two rings and magenta will be class C. Class D will be dashed blue.