Its a matter of personal preference.
There are two extremes. At one end, there is the law that can prohibit travel if you are deemed too drunk (unfit) to fly.
At the other end of the spectrum, alcohol dehydrates the body and combine this with the cabin atmosphere at altitude it doesn't make a good combination.
In short, drinking in moderation is acceptable. However its better for your well being avoiding alcohol intake all together before and during air travel.