license at 20? Which license? You can get your ppl at 17 ( which Im going to do) , CPL at 18 and ATPL at 21/22. Do you mean CPL at 20? I don`t think you can fly a 747/777 without an ATPL which you get at 21 or 22.
Also what lucky reason could happen? I mean you have to be at a high rank or so to be a pilot for widebodies.