"Researchers at an aerospace medicine institute report (in a study published in the journal Thorax) that consuming alcohol before or during flight—even as little as the equivalent of two beers—in hypobaric cabin conditions produces a simultaneous drop in blood oxygen saturation and a spike in heart rate in 100% of study participants. That paired physiological response, made worse by reclining or trying to nap, can create ideal “storm conditions” for a cardiac event, particularly for passengers with pre-existing pulmonary or cardiac vulnerabilities; the researchers also highlight that a large proportion of in-flight medical diversions are due to heart attacks (about 58%), underscoring the increased risk associated with drinking while flying." - Guy Martin