I wanted to design a huge alien organism that resembles something like a jet.
It lives on a low gravity planet that has 60% earth’s gravity and a similar atmosphere to earth.
It would fly by evolving a biological jet propulsion by using methane and hydrogen through bacteria that produces it.
It would be extremely resistant to UV radiation since it can fly as high as 80 km in the atmosphere and would be a filter feeder/predator that has extremely powerful periscope-like eyes that can see anything under it.
Is such a creature plausible (and if not, why not)? Can it find a way to fly without drag?
Note: there is a huge diversity of creatures that fly on this planet, which is why it would evolve.