My two commercial rigs have N numbers N600FC and N480FC. I own a couple that I don't use commercially, like my old DJI F550 "Flamewheel." and a Blade 350 QX, plus I am flying a test bird that I don't own. The first two would be impractical to get an N Number and a huge waste of time. The other I don't own and will eventually give back so I can't register it if I wanted it to. So this process keeps me legal to fly the noncommercial stuff.