You should never drink coffee or tea prepared on an airplane: You may get very sick. That’s the bottom line, according to recent studies by Hunter College’s NYC Food Safety Center about the safety of airplanes’ water tanks, which, it turns out, can be harboring some nasty contaminants such as E. coli and coliform. Some suggest you shouldn’t even wash your hands in on-board water. Airlines are only required to flush and clean their on-board water tanks four times a year. But when they fly to exotic destinations and get serviced between flights, they take on local water, which may not meet U.S. standards.