Someone named Adam recently posted an interesting question on the Ask a Flight Instructor website regarding any rules for or against the drinking of alcohol aboard a general aviation aircraft. Specifically he asked:
Is there a rule on passengers drinking alcohol in a light 2-6 seater aircraft? Is it the same reg as with a commercial aircraft? Passengers drink alcohol all day in commercial aircraft, is there any regs preventing my friends from drinking on board my small plane?
Kris Kortokrax responded by writing that there is no proscription concerning the drinking alcohol aboard a small plane. However, he also added that 91.17(b) says you cannot carry a person who appears to be intoxicated and this rule would likely limit how much alcohol could be consumed on a small plane. Kris also added that a pilot will need to consider what would happen in a potential emergency landing situation. Specifically, would you want your passengers to be sober or under the influence if they need to extricate you from the wreckage?
It would be interesting to note any UK or Europe specific rules regarding alcohol aboard an aircraft but then again, flying is different from boating or yachting. Hence, its probably best to leave the consumption of alcohol as an activity to do on the ground after a flight and away from the aircraft altogether.
Even more importantly – you are at least half an hour from the nearest bathroom.
That would be more the limiting factor in drinking aboard.
Personally, I'd leave it until I was on the ground.