Since air essentially behaves like a fluid, would it not be accurate to say, that aeroplanes swim through the air?

Fluid ≠ liquid. Gases and liquids are both fluids, as are plasmas. But swimming and drowning are ways of interacting with liquids specifically, not fluids generally.

Sure!

“Air acts like a fluid in that it moves and flows. A fluid is anything that flows. It is a substance that has no fixed shape and changes in response to external pressures. Fluids include liquids, gases, and plasma.”

And yes, you could say that a fish drowns in air. It can also drown in water, like the little goldfish kept in a bowl who never gets a refresher of oxygen into the water. It needs oxygen.

Aeroplanes can’t swim through the air for the same reason ships don’t swim through the water. Swimming implies propulsion through limbs, fins, tails, etc.

No, because it would be more accurate to say that air is a gas and water is a liquid. Propulsion methods are different for each.

If an airplane was light enough and had a gigantic surface area to mass ratio then it could slowly swim through the air. Such airplanes do exist. Take a look at tiny gnat flys. They do seem to swim through the air.

You can, and it would all be understood, but it’s not standard usage. Swimming is usually slower and using limbs to move as opposed to an engine of some sort.

The starSHIP Enterprise is in the air or space, but uses the term ship just like a seaworthy vessel.

Out of everything you gave as examples, drowning in air is the one I’ve heard before, or also sometimes suffocating in air to describe a fish dying outside of the water.