I'm not logged in, in order to look at the settings but, you use to be able to uncheck "use mount" and as result your chicken (toon) would run everywhere thus utilizing any speed boosts beneficial to the character.
I don't believe there is a distinction between ground/flight so unchecking it entirely would disable it entirely.
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Edit: I just looked, the option isn't there any longer. Try setting your 'Mount Distance' to a larger range (Default: 60).