I dunno. Lots of details suggests bending, especially earthbending, follows Newton's Third Law of Motion to some extent. Like when toph and aang use an earth slab as an elevator, they are "grabbing" onto the earth wall, or when zuko's bending failure blows him back. There's a lot of it in Bitter Work in particular.

Even Zaheer ostensibly obeyed physics by just blowing air around him.

What I'm saying is that bending a metal suit doesn't let you fly without something else to push against... but maybe a good sandbender could take flight in a sandstorm?