Mountain Air Cargo is a major operator of FedEx Express. FedEx’s Mountain Air Cargo fleet consists of the C208 and all FedEx ATR variants. They operate mostly in the eastern US, and somewhat in the Caribbean.
Their callsign is ‘Mountain’ and it should be added for realistic operation of the FedEx livery on the Cessna 208.
Here ya go @Cameron, just as you requested! :)