Travel and Leisure reports that there are three factors that contribute to the bad taste of coffee on airplanes: water, the brewing process and our taste buds.
First, the water used for coffee has been in the tanks for a long time, which means that it is not the freshest (or cleanest) water that could be used, according to "travel and leisure".
Second, the brewing process is another pitfall, as at 35.000 feet above the ground, water boils at a much lower temperature. Andrew Hetzel, a coffee quality and marketing consultant, explains that this disrupts the export process so that only some of the solid pieces of coffee can be dissolved.
Third, our perception of taste changes by about 30% when we fly, thanks to cabin pressure, dry air and altitude. However, there is a solution to this problem. If your coffee on the plane is very bitter, experts recommend adding a little salt, which will give it a slightly better taste.
Source: Sigma Live News