Just to summarise this in case anyone's confused:
In SmartView, to watch a fleet, we would usually use, to take UPS as another example, UPS* to capture all flight ID's starting UPS, whatever the registration of the aircraft
But some UPS flights don't have UPS as the frist three letters of the Flight ID, so using N*UP will find aircraft that have the 'standard" UPS N-number registration, whatever the flight ID.
This should capture pretty much all UPS flights, but still isn't guaranteed 100%, as some UPS flights will use a "wrong" flight ID AND have a "wrong" registration.
Rod