The drones must loose a big part of their payload capacity due to the high altitude, but it's impressive they can even fly there. Helicopters have a really hard time and planes need very long runways.
https://m.youtube.com/playlist?list=PL5Y2yyiC4P5QZLGC7SJcKwC...
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On another note, the Mars Helicopter drone worked just as well. It just had to ramp up to crazy rpm. I guess it's all about energy. 1m at sea level is about the same energy as 1m at Everest height. Drones can accelerate a lot so I guess 3x higher rpm (atm density is a third of sea level) is no problem.