I've transported a bunch of cargo, but don't know how to get "unknown cargo" or how to "fly a Clandistine Mission".

 

I'd like to try and earn those awards.

 

Can anyone help by telling me how to set things up to get either of them?

Clandestine cargo missions are at airports with no tower. (uncontrolled) They are somewhat "rare." There may be only one or two through the entire chain of islands at one time.

Look on the job board of the magenta airports (not the blue ones) and if you can't find any, change the date in the game and try again.

Thanks for the help. I now have that "Sneaky Guy" award.