Supernatural - as the word says - belongs outside the natural domain. That means, it obeys no laws of physics.
As long a phenomenon can be defined, measured and described by physics, it will not be supernatural. Of course, the physics may have to be defined first.
Deities defy any physics and are therefore supernatural.
How di Copertino can fly, is supernatural at this time. However, if it turns out to be some sort of story, a fraud, or explained physics - this phenomenon will turn "natural".