Comment by lelanthran

> A plane is not a fly and does not stay aloft like a fly, yet we describe what it does as flying despite the fact that it does not flap its wings.

Flying doesn't mean flapping, and the word has a long history of being used to describe inanimate objects moving through the air.

"A rock flies through the window, shattering it and spilling shards everywhere" - see?

OTOH, we have never used to word "swim" in the same way - "The rock hit the surface and swam to the bottom" is wrong!