A leaked briefing, reportedly issued by the carrier after a number of these events, warns pilots, “It could happen to you.”

British Airways has seen a rise in the number of fume events onboard its craft in recent months, leading the carrier to issue an advisory to its pilots regarding these incidents, reports the Express. A fume event happens when cabin air becomes contaminated by chemicals, smoke or other noxious substances.

The outlet reports that this warning was issued after the carrier logged 50 such smoke events in a single month.

A briefing leaked to the Sunday Times, as quoted by the Express, describes an incident that took place back in July on a flight from Cancun to London’s Gatwick Airport (LGW). During this particular incident, passengers reported feeling sick when a foul odor likened to “sweaty socks” filled the cabin. The briefing reports that travelers on the flight had to undergo medical checks upon landing in London.

The carrier reportedly issued a warning to pilots in training on the back of this incident, advising them that, “It [a fume event] could happen to you.”

An unnamed source also confirmed to the outlet that, “The number of fume events seem to have increased massively.”

Offering official comment on these kinds of events, a spokesperson for BA said, “We would not operate an aircraft if we believed it posed a health or safety risk to our customers or crew. We always encourage our colleagues to report any potential safety incidents, no matter how minor, to allow us to investigate them.”

“There has been substantial research into questions around cabin air quality over many years. In summary, the research has not shown that exposure to potential chemicals in the cabin causes long-term ill health,” the official added.