What is your suggestion?
ATC - Approach: Arrival sequence can be configured to choose which sizes, but not if they are pax or cargo. To remove this problem, I suggest adding something like a “Preferred type” choice to the panel.
How would it work in the game?
I think it could be implemented in many ways, but I suggest something like this as I think is pretty easy and UX accesible (see image).
Although they seem like buttons, I suggest them as being a switch, so when you try to activate the second to have both activated, the other will auto-deactivate.
Why is this a good idea?
Some players (like me) could be interested on cargo planes to level their airports faster with the XP cargo gives, or may be interested in wollar profits, so they would not prioritse cargo over pax.
To put an example, LHR has less cargo stands than pax, and you may want to rotate first your landing planes on cargo stands. The opposite happens at LEJ, where you barely have pax stands, so they take an important role in the airport.
This way, you could be focusing your efforts with landing ATC help.
Optional: Image or reference
to make sure my cargo is landed first to increase turnaround, but if it can be a direct function, that will be great.