[Economy] - convert to cargo

:bullseye: What is your suggestion?
Once a plane reaches the 4th Large maintanence check, the ability to convert the plane to a cargo aircraft would be possible (only for aircraft that have an available cargo variant)

:hammer_and_wrench: How would it work in the game?
the planes would operate like they already do as cargo aircraft, and for the UI, a Seperate button would be shown to convert the plane to a cargo aircraft, as this would be an option and not a requirement.

:balance_scale: Why is this a good idea?
this is something that happens a lot in real life (the entire existence of some cargo aircraft is due to this practice) and would also add another level of realism to the game

:camera_with_flash: Optional: Image or reference