Sasuke in flight:
He has chidori(which won't hit anything)
Chidori nagashi(which doesn't defend that well and he's not getting close to them)
Kirin(which needs clouds, a fireball, and time to get ready/ plus he wouldn't be close enough to hit them)
Snake summons(which can't fly and wouldn't hurt clay or sand)
He's flying on a hawk (which wouldn't be too troublesome to blow up or tear apart with sand arms)
Amaterasu(which Gaaras sand CAN block/ sasuke can't hit what he can't see and the sand can just be thrown away before it is burned away)
True Spear(which also won't reach)
Tsukiyomi(which is a weaker version and I doubt anyone will be looking at his eye/Deidara's eye can stop Genjutsu anyway)
Susanoo I figured it would kill his hawk lol
Deidara airborne:
Flying bombs of various speeds, power, sizes, and type
High Speed
Molecular bombs
His suicide
Experience fighting whilst flying
Gaara in the air:
Huge sand configurations which follow his will
Extra powerful sand(the sand in his gourd, because it soaks in his chakra it is faster and stronger)
Flying fighting experience(less than Deidara but more than Sasuke)
Can make more sand easily(even controlling half a desert)
I say Deidara owns sasuke Quickly(because he can't land) then the fight resumes from last time, but now Deidara has no citizens to hold hostage/
IMO Gaara takes it mid/high difficulty