it is usually used in positive way，it means "all is ready except what is crucial"

Christina I agree with Wang Haoyu. The sentence means: "Everything is ready, except for the most important and final favourable factor." Is it positive or negative? It depends on your perspective and the context. It also depends on your philosophy of life. Success has not been achieved, and 东风可能永不来。 It depends on who says it. If a university has been chasing you for a big donation that you don't want to give, and they put pressure on you, saying, "万事俱备，只欠东风", is that positive or negative? Perhaps neither. It's just a technique. 你的下属对你这么说，可能就是在为卸责而作铺垫。你的下属对政府官员这么说，可能在保护你，也可能在进行政治游说。 A blackmailer could say the same to you. She is ready to help you, but you have not paid the ransom yet. So it really depends on context.

in a positive应该是肯定句，in a negative是否定吧。可肯定和否定是指什么呢？英语中有词只用于肯定句，有些词只用否定句。但汉语的否定句应该怎么来定义呢？比如：他来。是肯定句，那么，他不来，就是否定句吗？他有一本书，肯定；他没有书，否定吗？如果这样来定义的话，那么我们也可以说： 现在我们还没有到万事具备，只欠东风的程度。这句话应该算否定吧。 汉语和英语不同，一个词语很少有绝对不能这样用，绝对不能那样的情况，所以，最好不要从只能用于肯定还是否定这样的角度去思考汉语的语法。

Christina Please do not mind some honest feedback. Your example "我假期做准备。我有我的票。我等待飞机。" does not show a correct understanding of "万事俱备，只欠东风"。 东风 refers to an uncertain crucial final favourable factor. A scheduled flight is not an uncertain crucial final favourable factor. 坐飞机去放假很平常，既不需要"万事俱备"的大阵仗，也不存在"最后关键性的一环"， 根本不用等待"东风"。 The other example is not quite right either. 罢工既成事实，你只是一个倒霉的旅客，那是bad luck, 不存在什么东风。假如你是资方谈判代表，经过多轮谈判，已向劳方提出了妥协方案，那么你就可以在电视访问中吹风施压，说"我们有很好的解决方案，我们认为大部分员工都热爱工作，愿意服务大家，现在呼吁工会理事们，以大局为重，领导我们的同事们复工，正是万事俱备，只欠东风，社会大众都期待着工友们的勇气和诚意。" 又假如，你花了五年时间筹备成立航空公司，但迟迟也拿不到政府批文，那才是有"万事俱备，只欠东风"之叹。

This phrase means lacking the crucial or the favorable circumstance is not on hand yet. It came from a story when all the war preparations were being made to burn the enemy's ships on the river. They were waiting for the vavorable East Wind to carry the fire in the right direction. Your example, does not show the most crucial factor in the flight... If you were to say, "My soul is ready, my body is willing, alas if not for my empty pockets, my vacation would be perfect..." 心有欲, 身亦願, 万事俱备, 只欠東風吹來金錢袋". The literal translation is "my heart is desirous, my body is willing, everything's prepared except the lack of the East Wind blowing a bagful of money to me (windfall)."