dragonfly

When I was walking on the machine in the fitness center, I saw dragonflies over the window.
How they can fly in that height?
It's fifth floor.
And they fly higher and higher.

How high they can fly? 100m? 200m?
and How about birds?

If they fly higher then there is less air density and air pressure.

They also should energy efficiency and breathing because of Oxyzen density and pressure.

If human clime a high mountain like rocky's mountains, some human will get mountain sickness.