Turns out, the water used in the coffee is the same water used for plane toilets and can contain dangerous bacteria such as E.coli according to a flight attendant.
Speaking to Vice, the anonymous flight attendant who is said to work for a major American airline issued a warning to travellers: 'Don't drink the coffee on airplanes.'
They further added: 'It’s the same potable [safe to drink] water that goes through the bathroom system.'
'We recently had a test for E. coli in our water and it didn’t pass, and then maintenance came on and hit a couple buttons and it passed.'
A spokesperson has since gone on to deny the claims: 'There is absolutely no chance of any cross contamination due to the system’s plumbing design. This is common place amongst most aircraft manufacturers and airlines. Fresh water is loaded onto the aircraft daily.'
Another flight attendant who works for American Airlines although made a shocking revelation to Travel + Leisure magazine that the water tanks on the aircraft 'are probably only cleaned out every six months to a year'.
If there's anything to make of this, it’s probably best to have a coffee while at the airport when travelling.