Flying Feature in MMORPG Help (similar to wow mounts)

Hi guys im making a MMORPG using the atavism plugin, and i wanted to add a flight feature, i haven't done anything with movement on the Z axis yet, so i thought i would come and ask for the best practise.

initially what i wanted to do is: when the spacebar is pressed (only once the character would jump and play an animation) (if it is held down it will start to fly)

the tricky part i feel is where i want the character to not decend when spacebar is not being pressed but just levitate in the current X,Y,Z similar to the way wows mounts/druids flight form. work. but the character alone playing different animations.(the animations part i can prolly figure out easily just this part i'm stuck on)

 

So you haven't even made your player move forward.