I remember books where Raptors literally fall through the atmosphere. I dunno if Hawks can specifically fly better or higher, but I do know they wouldn't ground slam.
I know a bit off topic, but I would love to see a vibro cannon be in game for those tanks and fortresses. Was one of those under used weapons in TT specially in the old version(the one with sustained fire dice). Once played a large IG mobile army and took 4 of them 3 turns later Eldar win.
They can do a ground slam just fine, they just drop a satchel charge instead of themselves A Vibro Cannon would be a fun addition, but we probably won't see it for a long time We will however see the Distortion Cannon at launch, since the Warp Hunter is confirmed and will probably be our "anti-fortification" vehicle, though I always viewed it more like a Tank Hunter... It is so sad that Mymeara isn't in the game, since they are known to use them a lot.
Funny thing, in the current rules the Warp Hunter isn't that big of a destroyer as it used to, not even a tank hunter. It's now more of a moderately heavy artillery piece (weapon: s6, 3 small blasts(or 1 template), barrage, distort (wound/pen anything on 6)). It used to be D. I hope they make it D in the game, with amazing visual effects.