Actually, coffee isn't the only thing you should avoid drinking on airplanes, you should also pass on the tea, or anything that uses water that didn't come from a sealed bottle! A study conducted by The Food Policy Center at Hunter College in New York City found that the water tanks on planes are not cleaned very often. They're just topped off with new water after every flight so water has been sitting in the bottom. Another study, this time from the EPA found that 12% of commercial planes also tested positive for fecal bacteria in the top water, which is used for not only making tea and coffee, but also the water you use to wash your hands. My suggestion? Only drink bottled water and bring hand sanitizer on airplanes!