You may need to just increase the values of the air control variables. I’m not on my dev PC, but, it’s in the Character Movement Component. Increase the “Air Control” from 0 to 1 and then increase as well the “Air Boost Multiplier.” You may also want to increase the “Air Braking” (I think that’s the variable name?) so he’s less “drifty” in the air.
Keep in mind, these controls only work as long as your giving vales in the “Add Movement Input” node. Otherwise, Unreal will think the character is in air but “decelerating” since no “forward” movement input is given.
Hope this helps!