Ok I have also HEARD that it is possible to get the last 2 pieces and upgrade your chocobo before getting the airship, but that it will turn the Blue Narciss into the airship and skip you over a large section of disc three. I am currently on a playthrough ( old games erased that were before airship ) to find out if this is true. If you want to beat everything in the game make sure to go through and get the airship before getting the last two chocograph pieces etc.