Most electrical planes flying today will have around 160-200 wh/kg of battery. That's not a lot but somebody is buying them nonetheless. The reason for that relatively modest energy density is that anything flying and certified now would have entered the certification process many years ago. The question is not if those batteries can be improved but by how much.

Tesla already has cars on the road with batteries doing better than that. Their upcoming 4680 battery cells will be around 380 wh/kg, apparently. Then there are several companies working on solid state batteries promising closer to 500-600 wh/kg. Sounds good? That's 2-3 x the range of electrical planes on the market now or very soon. There's nothing to be skeptical about here. Pretty much a done deal. With that type of battery, we'll be seeing planes do 400-800miles; possibly a bit more. If you think that's ludicrous, the Eviation Alice is currently pre-selling a plane that will do 440 miles. Apparently, they use 260 Wh/kg batteries currently. Upgrading to something with 500 wh/kg would pretty much get them close to a 1000 mile range.

I consider 2x to be the minimum of what we can expect this decade. That's just a matter of updating these planes with batteries that are either already being produced or will be very soon. More a matter of when than if, really. These are first generation planes too. It's not a question of if they will improve but how quickly and by how much. Designs, engines, wiring, materials, etc. There still is a lot of room for improvements.

Longer term, I'd say 4-6x current ranges should almost certainly be doable based on just battery improvements. My view: 4x would be disappointing. 6x is a good number to shoot for longer term and we can actually hope for more. Like 8-10x. But actually 3x current ranges would already be a game changer. We'll see.