That same code does define "aircraft" as: "any contrivance invented, used, or designed to navigate, or fly in, the air."
I don't quarrel with your understanding of the U.S. Code. But that doesn't change the fact that the Tenth Amendment makes this law null and void. I know that's something many of our enlightened neighbors have no concern for anymore, that whole checks and balances and laws created by local representatives from your area who better understand your location and priorities and values and such. But despite it being ignored, that's the law in the system that has been set up, and repeated abuse of that law doesn't change the law. Nowhere in the Constitution is Congress given the power to regulate "any contrivance invented, used, or designed to navigate, or fly in, the air." Therefore, that is a State issue to be addressed and any attempt to regulate it is overreach.
The Commerce Clause makes interstate flights fair game for the feds, and for good reason, but I don't know many drone operators who are carrying passengers from DAL to LAX. Joe Schmoe in his backyard or at the local park? That is NOT something the federal government has any jurisdiction or authority over.