So...
I used this image to try to find the shortest route from start to finish. Assuming you don't use any warp whistles, hammers or clouds, excluding hammer bros. and piranha plants, it looks like you must play through 72 levels.
Remember that after losing a life in a Koopaling battle, it makes the airship fly through the map, and sometimes if it stops in a locked path, you must play through the level blocking it.
Getting a game over undoes every level in the current world (However, if you beat a fortress, you get a shortcut, but it still makes you play a couple of levels again).
Yeah, this game was quite something.








