Your definition of "clearly" is very different than most people's I think...
It also differs considerably from what is found in federal law. 14CFR1:
1.1 General definitions. Aircraft means a device that is used or intended to be used for flight in the air.
That says nothing about carrying people. The difference between airCRAFT and airPLANE is also clear, same section:
Airplane means an engine-driven fixed-wing aircraft heavier than air, that is supported in flight by the dynamic reaction of the air against its wings.
The airPLANE is a fixed-wing heavier than air airCRAFT. That means that airCRAFT includes hot air balloon, gliders, and yes, drones.
And even the definition of airplane does not include a requirement that people be aboard.
But wait, quadcopters aren't fixed-wing, so are they covered?
Helicopter means a rotorcraft that, for its horizontal motion, depends principally on its engine-driven rotors.
So drones are helicopters, unless they're the fixed wing version. And gosh if the FAA doesn't have the authority to regulate flight of helicopters.
Now what about this "high altitude" limit on the authority of the FAA? Sorry. That's just nonsense. There is well-established case law that the FAA can (and does) regulate the use of aircraft down to the surface. 14CFR91 is the federal law covering general operating and flight regulations, and is applicable as follows:
(a) Except as provided in paragraphs (b) and (c) of this section and ÂÂ91.701 and 91.703, this part prescribes rules governing the operation of aircraft (other than moored balloons, kites, unmanned rockets, and unmanned free balloons, which are governed by part 101 of this chapter, and ultralight vehicles operated in accordance with part 103 of this chapter) within the United States, including the waters within 3 nautical miles of the U.S. coast.
Notice that "aircraft" clearly includes kites and even moored balloons, because these had to be specifically exempted from coverage by this part that covers "aircraft".
And 14CFR91 contains rules that apply to aircraft all the way to the surface of the earth. For example, Class B, C, and D airspace extends from the surface up to the specified altitude (it differs), and the "Mode C Veil" extends from the surface up to 10,000 MSL for a distance of 30 miles from the applicable airport. Thirty miles. And 14CFR91.131 clearly says:
91.131 Operations in Class B airspace.
(a) Operating rules. No person may operate an aircraft within a Class B airspace area except in compliance with Â91.129 and the following rules:
That kinds makes it clear that the FAA has authority to regulate aircraft from the surface. That cite is just one example of many.
There is no "high altitude" limitation to the rules, and the only reference to "high altitude" that I know of deals with a class of VOR that has a "Standard High Altitude Service Volume". The only thing that "high altitude" might refer to is as a lay description of Class A airspace, which runs from 18,000 feet MSL up to flight level 600 (about 60,000 feet MSL). Note that there are also Class B, C, D, E, and G airspaces which the FAA regulates, so there is a lot of precedent for FAA regulation well below "high altitude". Many of the FAA rules contain an exemption similar to "except as required for landing or takeoff", which also make it clear that the FAA has the authority to regulate aircraft activity at well below "high altitudes", since landings almost never occur at high altitude.
Your argument really feels like the kind of games sovereign citizens and other conspiracy theorists play
Yes. Loopholes based on lay use of terms that are specifically defined in the regulations.