Now flying on the airlines is stressful enough, and a nice cup of tea or coffee once you sit down on the plane might make you feel better, but this is why you should never EVER drink the coffee or tea on any airliner, anywhere!
Let’s start with where the water comes from.
It comes from your regular city water pipes, which depending on what hub you’re in, may or may not be a good thing (probably is a bad thing). The water is then put into a dirty rusty weird looking truck, unfiltered, and sits in a dirty tank on the truck that is rarely cleaned.
After this truck sits out in the nice warm bacteria loving weather, it will be called over to an aircraft in need of some “potable” water. The truck then connects a dirty hose that dirt, spilt jet fuel, and spilt blue juice from the lavatories has inevitably gotten into a bit, and proceeds to pump the questionable water from the dirty truck, through the dirty hose, into the very very very dirty water tank of the aircraft in question. These tanks NEVER get cleaned. Many of them are in service for years without seeing a bit of a brush and some disinfectant.
Once the questionable so called “potable water” has be pumped into the airplane, it will then be dispensed into a very old and disgusting coffee pot, as either hot water for tea or coffee. The water being heated helps to dissolve all the other nasty sediment into the water, before it leaves the pipes that have never been cleaned, and into the coffee pot.
Eventually this goo is brought to you, disguised as a dark liquid called coffee (or tea). Bon appetite.