being tripped with fly.

[Sub_Zero]

Maybe I'm missing some important rule, but if this is the rule for tripping:

"Some creatures—such as oozes, creatures without legs, and flying creatures—cannot be tripped."

why do creatures like dragons have cmd modifiers that specify their trip CMD?

[KahnyaGnorc]

That's for when they are not flying.

[Fomsie]

Right, just because something can fly, doesn't mean they are.

[Sub_Zero]

So the flying creatures are immune to tripping only applies when they're actually flying? Wow, that means that my groups been playing that wrong for years. I read that as, creatures with flying cannot be tripped, instead of, when they're flying they cannot be tripped.

[Claxon]

Yeah, flying creatures are only immune to being tripped while flying...

However, at least in the home games I play in it's assumed any creature capable of making the DC 15 fly check is always hovering and never touches the ground except to sleep. It renders them immune to trip and all sorts of other terrestrially based hazards.