They deliver enormous range and endurance figures without heavy batteries, and they mirror the approach Airbus and others are taking with commercial airliners.

Batteries weigh aircraft down, they can heat up, and they take a long time to charge – but they're very simple, easy to use, and they store enough energy for many use cases. Hydrogen is a pain in the butt at every step of the way, but used in a fuel cell powertrain it carries so much more energy than lithium batteries for the weight it costs that you can keep your aircraft flying for ridiculous lengths of time.

To illustrate, back in 2020, we compared the world record endurance flights of multicopter drones running on pure battery power (1 hour, 51 minutes), a 16-liter gasoline-electric hybrid system (10 hours, 14 minutes), and a hideously ugly hydrogen fuel cell system fed by 6 liters of gas (12 hours, 7 minutes). If range and endurance are your priority, batteries don't come close to hydrogen.

And while it's possible to stick the hydrogen tanks and fuel cells in the middle of an airframe, where the combustion powertrain or battery pack would normally live, there's a few reasons why you might not want to. Hydrogen weighs less than batteries, but takes up a lot of volume. You might want to dedicate that space to cargo, for starters. Or, if you're talking about a bigger airframe, passengers. If you're talking about passengers, there might be some psychological value in having the hydrogen stored well away from the cabin, and putting the whole system out on the wing probably helps with cooling and airflow as well.