Contentious subject, cabin air. While some studies suggest it is no more germ-laden than the air in, say, a large office, other research has found it to contain toxins linked to cancer, chronic fatigue and neurological problems.
Such studies are not as contradictory as they seem; it is, for example, possible to catch the flu on a flight without breathing in toxins - and vice versa, the Telegraph reported.
To understand why is to understand where the air you're breathing at 35,000 feet comes from; half is "recycled" from the cabin and half is "fresh air" drawn in from the engines (all of which is pushed through filters to remove any microbes and toxins).
There is some debate as to how effective those filters have been; according to the World Health Organisation (WHO), in 2015 more than 3.5 billion passengers and 500,000 pilots and cabin crew were exposed to low levels of engine oils in the air. Plane manufacturers, however, maintain cabin air is safe to breathe.
Either way, researchers claim the best way to avoiding catching a cold from a fellow passenger is to keep the air vent above your seat open and allow yourself to be buffeted by filtered air.