Should You Be Concerned If You See Fog Inside An Airplane?

Even though airplanes aren't always foolproof, they statistically remain the safest form of travel out there. Nevertheless, it's easy for the mind to conjure up horrifying scenarios at the slightest strange occurence. For instance, if you were to see a cloud of fog fill up your flight, you jump to the conclusion that your plane is experiencing a major malfunction and that your final moments will be asphyxiating thousands of feet in the air. Thankfully, this particular occurence is far more common — and way less dangerous — than you might expect. 

A cloud of white fog appearing inside your flight before it takes off is more than likely your plane reacting to the temperature outside. When a plane's doors and vents are open before flying, outside air will naturally enter and interact with the air inside. If you're traveling during the warmer months of the year, this means that the hot or humid air from outside will mingle with the naturally cooler temperatures that airplanes are kept at for optimal comfort. This clash results in condensation, the same naturally occurring scientific reaction that occurs when you see your breath on a cold day. And even if you simply find the fog to be annoying, the good news is that it typically only lasts a few seconds before dissipating and won't occur on the flight itself.  

While fog or mist appearing in your flight is a relatively regular occurence, other similar instances may rightfully warrant some concern. In particular, seeing or smelling smoke could be an indicator of something more serious and shouldn't be ignored.

There are times when such occurrences aren't cause for worry. For example, as some flights prepare to take off, it's not uncommon for passengers to detect what smells like something burning. This can often be attributed to a small rear turbine engine known as the auxiliary power unit (APU). Made to activate the plane's electrical system and air conditioning before taking off, the APU may release a burning smell that comes from air being sucked into the rotors. However, like the fog that comes from condensation, this is typically a short-lived occurence and not harmful in such brief instances. 

A potentially more serious sign to take note of is if you see smoke appear alongside any bizarre odors. This can be an indicator of electrical issues, fuel leaks, or even a cabin fire. While thankfully uncommon, it's crucial that you stay alert of any noteworthy disturbances and inform crew members as soon as possible.