To be extra safe, the CUNY researchers advised people never to drink water onboard a plane that does not come from a sealed bottle. They also said passengers should not drink coffee or tea brewed on their flight, and that they should even use hand sanitizer instead of washing their hands with onboard water.

In 2026, health experts and flight crews continue to warn against three specific beverages: tap water, excessive alcohol, and heavy caffeine. The tap water on planes (often used for coffee and tea) is stored in tanks that, despite strict regulations, can harbor bacteria like E. coli. It is always safer to stick to bottled water or canned drinks. Alcohol is another major concern; because the air in a plane cabin is significantly drier and the pressure is lower, your blood oxygen levels drop, making the effects of alcohol two to three times more potent than on the ground. This leads to faster dehydration and increased heart strain, especially on long-haul flights. Finally, while a coffee might seem necessary for a red-eye, the combination of caffeine and the dry cabin air can lead to "jittery" dehydration and disrupted sleep patterns, making it much harder for your body to adjust to new time zones upon arrival.