I am so impressed with this, seriously. It's poni through and through to the point where I can't find anything wrong in that regard. You got the characters right, the runcycles right the look–and–feel right, the composition right;This is how pony should pony pony.Issue–wise, there's not a whole lot I'd really complain about. RD's sorta missing her lower jaw a bit [compare her nose definition to her jaw], her mane tangents into her left wing, and she's missing that little line that goes in her ear.I think you could make better use of her wings, too. Currently, they're just sorta there. What you may consider doing is using them more actively — f.ex here, have her using them to aid her movements, by way of cupping, angling, etc. She's a top–tier flier, so it's sorta weird that they'd just be uselessly flared out like that.Mind, I don't know a whole lot about flight dynamics, but you could pester Kits or the internets in general probably. Basically though, it's a third set of appendages, much like our own arms,fancy iron–on decorations.So using them as such can add a lot to a character, and a pic in general.