It depends on the context.
I'm talking about Peter Pan style flying and how it'd break suspension of disbelief. Like if they suddenly show an Elf not only being able to jump far, but literally change directions in the air. That would break all sorts of rules that have been established so far with what we understand of their physiology.
I'm not sure exactly what you're talking about and the context of it as it pertains to Tolkien's own writings. If we're talking about flying ships and whatnot, then that may be implied to be magical/technological, and we know that magical enchantments do exist in the world such as rings that grant one invisibility. It doesn't mean flight or invisibility are a natural part of a being's physiology.