But yeah, to make a big carbon impact, electric planes would definitely need fast turnaround.

Most charter flights are just to fly to somewhere nearby, drop someone off, fly somewhere else pick someone else up, repeat. Often the destination is some small airport that doesn't have jet fuel (most charter aircraft are turboprops) so you need enough fuel for the return leg or you make a 30min detour to somewhere that does.

The hops are often small but you often need to do many of them back to back without a ton of downtime in between and usage patterns tend to be not well distributed (not much happens on a Tuesday but on a Friday every rich banker is trying to charter a flight to their house on Nantucket or wherever). It's basically the same usage pattern as an uber vehicle will see only the vehicle itself is a proportionately larger cost so you can't as easily just have more of them to make up for charging time (like some electric bus fleets do).

Charter flights are one of the last things I can see being electrified unless battery swaps become a thing because the charging time directly hits profitability.