Should I avoid alcohol on a plane?
Does drinking alcohol during a flight increase its effects?
Although your blood alcohol reading will be the same after that second glass of wine whether you're flying high or standing by the barbecue, you will probably feel its effects more in the air.
A clinical trial performed on 10 healthy male alpinists in Austria found that their blood alcohol content was the same for a given amount of alcohol, whether it was consumed at an altitude of 171 metres or 3000 metres.
However aircraft cabins are pressurised to an altitude of that higher figure.
This is enough to experience some symptoms of altitude sickness, which can include nausea, fatigue, an unsteady gait and headache, all similar to the symptoms of over-consumption of alcohol.
Even though your blood alcohol level might be the same inflight as at the dinner table, the effects of drinking might be more pronounced because you're getting a double shot - alcohol plus altitude.
Altitude sickness will not usually manifest until several hours into a flight.
Hit the booze early on and unsteadiness, lethargy and nausea might continue to increase even though you stopped drinking a couple of hours before.
The Austrian trial concludes "Caution in the use of alcoholic beverages at moderate altitude is therefore necessary."