I thought about doing this when I was playing with lifters a couple decades ago. The idea was that you could ionize the boundary layer, to make it somewhat "self repulsive", to thin it, to try to reduce the skin friction drag [1].

I remember doing some napkin math, and the added weight/power would be a net loss.

1. https://en.wikipedia.org/wiki/Skin_friction_drag

Accelerating the ‘plain air’ isn’t really necessary to the propulsion. Once you’ve accelerated the ions you’ve already accomplished a momentum transfer - if those ions then go and share that momentum with some non ionized air molecules that’s their own business.

I guess maybe the non ionized air acts to keep the ions around between the two charged grids for longer, which means that for each ion you create you can maybe exploit its attractive/repulsive force for longer?