green slime said:
but back to the hijack: to me it seems obvious that "flavour text" is what is causing the confusion.
I agree.
The MM says you can run when flying and the a character' speed doubles with ER.
It is only the flavor text in the PHB that is a problem. Even in the PHB the spell says "Your speed and max jump dist. doubles".
It seems as if the speed works on all movement rates.