Nice job on the f-air. It looks a lot better than it did (seeing 16->17->18 made me wtflol at the awkward movements). I would maybe suggest adjusting frame 16 to lie closer to 15's position, and adjust 17's arm position to be close to where 16's currently is on the Y-axis, but keep the fist centralized on the Z-axis (giving 17 the furthest reach of the animation, and 17 along with the interpolated frame 18's hitboxes being max range on the attack).
Or perhaps bring 17 a little closer to 18's position, and also 18 further away from 19 and slightly closer to 17 and make 16 the maximum range.
The difference between 15 and 16 is a huge range of movement, then 16 and 17 are very similar, then 17 to 18 is another huge change, and 18 to 19 are again very similar, so it looks a bit strange imo.