Congratz on reaching your personal best! I noticed that your aperture is a little too high which may be the reason why so many comments on the "underexposure". Try bringing your aperture down to f/5.6
This is neat. It's got tremendous movement in it. Your focus is spot on. Very well done. I might like to see the underside of the wing just a little brighter. Great detail there that's hard to make out.
Very nice capture of flight and good placement in the frame. This seems to be just a tad underexposed - try adjusting levels or adding a bit of brightness - it'll bring out the bird better and brighten up the slight dullness of the sky.