Is there any kind of developmental proof of 3 fold improvements every decade or so in energy density?
I'm getting so tired of this whole approach to the modern world "we're building a cool thing, we don't know how to power it, but some day someone will!" Why stop with airplanes, let's build teleporters and warp drives; they're theoretically possible - just need the technology to catch up
^that said, I like Diamond aircraft and their approach with the diesel engines, the DA62, DA50, etc., lend them credibility. But as has been stated before "up to 90 minutes" is not useful for general aviation outside of a niche market (training, coastal sightseeing tours, etc.)
There's a universal belief among proponents of the world's adaptation of battery supported utility generation and transportation there will soon be a magical gain in the energy density of batteries.
This belief has caused governments to require that utilities abandon thermal power generation, and vehicle manufacturers to transition to battery powered products, with looming deadlines in less then ten years.
The folly of this premature rush to untried and unreliable power generation and storage sources is being revealed right now, as the shutdown of thermal power generation and a dearth of wind currents across the North Sea and Europe has created a severe and dangerous shortage of electrical capacity.
As winter approaches, coal and natural gas supplies are at historical lows, and prices have increased fivefold. This is a preview of what will occur when reliance on wind and solar, backed by inadequate battery storage capabilities, replaces thermal power generation sources that are unaffected by the vageries of weather.
The anticipated wholesale adaptation of battery powered vehicles has critical weaknesses that are being ignored. A primary issue is how the quantity of raw materials needed to produce millions of batteries will be sourced. Many of the components are mined from the earth, and it will take years for those facilities to be designed, environmental studies done, and supply chains to be established.
There are political issues that must be resolved. Secondarily, there have been studies done that show demands on the electrical grid which will occur when the number of battery powered vehicles proliferate may result in widespread overload, outages, and failures. Upgrades and expansion of the grid will take many years to accomplish.
This headlong rush to the future, with serious questions about the wisdom of it being ignored, has dangers.