in the previous halos, you had a bit of control as to how you moved in mid air, but not much.
then came the jet-pack in reach and you could float around where you wanted. but people seem to think that will break maps when combined with sprint in halo 4, which TBH i can understand and fully agree with as an observation.
but what if the jet-pack in halo 4 is actually a jump-pack and behaves exactly like your jump button, but can be used mid air, more of a double-jump like in unreal tournament than a jet-pack.
which is where air control comes into this, if you are running and jump, you keep travelling in the same direction, if you hold backwards and jump you jump backwards. but if falling (from the spire lets say) you would have control over what direction you fall (like a sky diver, they do not fall straight vertical)
now with what i just said imagine a double jump, you run at a wall too high to jump over/onto so you jump then mid air, still holding forwards you use the jump-pack and jump again, this time onto/over the wall, but unlike the jet-pack, you lost momentum during your first jump so your second jump moved slower. or if you wanted to you could run, jump, then hold backwards not affecting your momentum for the first jump, but when you double-jump you go backwards like you would if you jumped backwards from standing.
the limits of how high/far you can jump are still predictable and not massive, while adding some more choice on how to engage a fight, or get to an objective without leaving you vulnerably floating through the air, and to improve this, it uses all its charge in one go, and has to fully recharge before used again, like hologram in reach.