It's a phenomenon you might be familiar with if you've ever boarded an airplane on a humid day. Hot, muggy air from the outside meets the cool air on the inside that's blasting from the aircraft air conditioning vents – temporarily creating what looks like mist or fog inside the cabin. Recently, TikTok user Savannah Gowarty posted a video of inflight mist and condensation on a domestic US flight.

The video garnered over 13.1 million views, with amazed and confused commentators questioning what was going on. Short answer: it's a natural occurrence that usually only lasts a short while, and it's nothing to worry about.

READ MORE: Why you should never tie a ribbon to your suitcase - according to a baggage handler "On hot and relatively humid days, cold air from the aircraft's air conditioning system mixes with the warmer, humid cabin air and lowers it to the dew point, creating fog," a Federal Aviation Administration (FAA) spokesperson tells CNN Travel. "The fog is generally short-lived as the cooled air quickly warms above the dew point." READ MORE: Destination dupes: Domestic Aussie holiday spots to substitute for overseas trips When an airplane is waiting on the ground pre-departure, the aircraft cabin air is kept cool "either from an external ground air conditioning unit or the aircraft's own Auxiliary Power Unit (APU)," as the FAA spokesperson explains.

"Both provide cold air (usually much cooler than the ambient temperature) which can temporarily lower the dew point of t.