I have noticed that the website interface of FlightAware shows information about IFR flights, but limited VFR data. Aircraft on VFR “radar flight-following” only show on the maps, with their tail number, altitude, and speed. This implies that their lattitude and longitude is known and is in the system somewhere, though it cannot be accessed by searching for the tail number (no flight plan).
Can these VFR aircraft be accessed through FlightXML? At least the location?