Tap Water (Including in Coffee and Tea) As T+L previously explained, the water tanks on planes are notoriously grimy. A 2004 EPA sample of 158 planes found that 13 percent contained coliform, and two had dangerous levels of E. coli.

You should avoid ordering coffee or tea on an airplane primarily because the water comes from the aircraft's onboard storage tanks, not from a bottle. Multiple studies, including the 2026 Airline Water Study, have shown that these tanks are rarely scrubbed and can be breeding grounds for bacteria like coliform and even E. coli. While the water is heated to make your beverage, it often does not reach a full rolling boil long enough to neutralize all pathogens, especially at high altitudes where the boiling point of water is lower. Furthermore, the hoses used to fill these tanks at various airports around the world are themselves prone to contamination. Many flight attendants famously skip the "hot water" service for this exact reason, choosing instead to drink only bottled water or canned sodas. If you absolutely need a caffeine fix, it is much safer to buy a cup of coffee at a Starbucks or airport cafe before you board, or to bring a sealed bottle of cold brew in your carry-on.