Ohoneandahalf

I was under my car the other day inspecting my exhaust and driveshaft thanks to road debris, and I noticed there is another line that runs from the fuel tank to the engine bay (or isa versa). The little line is the the one that goes to the fuel rail, but where does the big one go and what is it for? It's probably twice as big as the little one and it says "fuel" on the line. Ford made the fuel system returnless right...?

mustang_montana

what year is your car? mine is return style and the newer ones are returnless