48 feet of road bed width is what is needed.
If 48 feet of road bed is all that's needed, for how long does the mountain road bed need to be straight and somewhat level for the 777 to safely land on it? Are any special accommodations required for the airplane's wings on the mountain landing strip you propose?
And a roadbed thick enough to handle 160-plus tons of aircraft landing on it at over 100 miles per hour.