This conclusion seems fairly straightforward–altitude exacerbates physical levels of intoxication if alcohol is consumed in high enough quantities–but subsequent studies have cast some doubt on it. A 1985 study showed that response potential was impaired by alcohol, but did not differ with altitude as the study was conducted at two locations with altitudes of 5,280 and 14,264 feet respectively. Later, a 1988 FAA study on alcohol and pilot performance once again noted that inebriation impaired performance, but “no significant effects on performance were obtained due to altitude or to the interaction of altitude with alcohol.” The same authors also noted in a separate study that breathalyzer scores did not indicate any synergies between altitude and alcohol intoxication. The evidence for a change in blood alcohol content with altitude is hardly conclusive.
Since the first round of FAA studies conducted in the seventies and eighties, the question has not been reexamined in depth. Perhaps government funding considers this a moot point—pilots shouldn’t be drunk in the first place, why measure if it matters how high they are drunk? While we may not have solid answers as to if the myth is true or not, we can still ask why it would even be true in the first place?
Some have suggested that we feel drunker at high altitude because both alcohol and low ambient pressure dehydrate the human body. Airplanes have humidity levels under 20%, and the booze we drink is a diuretic, encouraging urination. While this may indeed magnify dehydration, it is unlikely that this influences blood alcohol content significantly. Others have said that human metabolism slows down at higher altitudes. Thus, the body processes alcohol at a slower rate, and it stays in the blood longer. This also seems untrue; even the 1970 study which concluded that high doses at high altitudes produced higher BAC, showed that, after peaking higher, the body then metabolized the alcohol at the usual rate. A somewhat more likely possibility is that low ambient pressure helps air in our bodies expand, effectively increasing the ability of the stomach and intestine to absorb alcohol. While some of these may explain the physiological aspects of intoxication, our perceptions of drunkenness may be explained otherwise.
The environment within a plane, regardless of altitude, likely impacts how we feel, particularly when we drink. Some evidence points to synergies between the experience of G force and alcoholic intoxication; mental performance decreases when the two are combined. The movements of the plane, too, help to disorient us, nauseate us, and keep our eyes moving. When we get up from our seat after 2 hours of asking the flight attendant for whiskey-and-cokes, we may feel more drunk simply because it is difficult to walk down such a small aisle in a vehicle that can move on three axes. In fact, the body is constantly trying to monitor the yaw and the pitch of the aircraft which can be disorienting while sober. Lastly, hypoxia, or lack of oxygen, may contribute to the nuanced sensation of drinking on a plane. Alcohol consumption can actually make it harder for the body to adapt to low oxygen environments.
Before boarding your next flight, think twice before echoing this well-traveled tall-tale. Believing that we get drunker on fewer drinks up at cruising altitude definitely adds to the romantic notions of being served complimentary wine or beer, but it might just be false. That is not to say drunkenness in flight does not feel different than usual. Being enclosed in a fuselage in the sky with no escape escalates the risks associated with drunken behavior without a doubt. For this reason, airlines should always ration their drink service to passengers. Nevertheless, it is great news that in-flight alcohol is coming back.
