Daedalus' plan was a good one because it resulted to him successfully escaping from the island. At that moment, I think that his plan was thought of well and very clever because when you try to think of it, if he had chose another plan that involved land, he could easily be killed since the place was King Minus' territory. The plan may seem like a failure because Icarus died, but it's not. That was because of his recklessness and carefree attitude. He forgot his father's words which led to his unfortunate death.