>A bonus: The airplane can regenerate energy during braking, just as electric cars do. When the pilot slows down or descends, the propeller becomes a windmill, running the motor as a generator to recharge the batteries. In the sort of airport traffic pattern typical for general aviation and student-pilot training, this energy savings comes to about 13 percent. In other words, if a plane lands having apparently used 8.7 kWh during the flight, it has actually used 10 kWh⁠—the propeller-recoup system put back roughly 1.3 kWh while flying in the traffic pattern.

I think the issue is that by the time you are on descent, the flight is nearing an end, so the benefits for range extension aren't great.

Not really. You take the potential energy stored in the airplane and use it to transit to the airport. On my (gasoline) airplane, I fly most of the descent under significant positive thrust/power (150+ HP worth of positive power, often over 200 HP).

The only time I could see wanting net regenerative power is on very short final (the last 50 feet of descent) or for braking on the runway (especially on contaminated runways). But neither of those will be effective for regen/extending range.

Maybe they could install bicycle cranks so the pilot and passengers can all pedal their way through the air.

Yes, the props rotate backwards - it's called windmilling.