Skyborn (2012)

Stranded in a foggy post-apocalyptic wasteland, a father Gideon and his son Blue build a flying machine to see above the clouds. But Blue is fed up with his father's crackpot dream: their flying attempts are becoming too dangerous, and he is sure there is nothing but cloud in the sky. So Blue hatches a devious plan to keep his father on the ground.

Unfortunately the movie Skyborn is not yet available on HBO Max.