if your flight is 4+ hours.. go ahead. i just got back from syria (from los angeles. it was 11 hours to amsterdam, 5 hours in schipol, and 5 1/2 hours to damascus..) i was tipsy before the plane even took off.. 11 gin and tonics, 4 scotch and cokes, 3 huge cups of cognac, and 4 cups of baileys (the cute french girl next to me liked baileys... and the stewardess was a pro drink mixer)..... and that was just from LAX to schipol.. i have to admit it was the best flight of my life. if its a short flight and you're alone you may regret it.. people tend to forget certain important things when their under the influence.