Fog can be induced by aircraft. I quote just one example.

I was based at Strubby, Lincs in the late 1960's operating Varsity
aircraft (large twin pistons). One winter's morning, it was fine,
windless and relatively clear but obviously very close to being foggy.
Our met man Max (Meekin? A Pole or Czech who never lost his accent)
had briefed us that fog was quite possible.

Anyway, as soon as the first Varsity started an engine, the stirring
of the air put the whole airfield in fog (circa 100 metres vis) in a
matter of seconds. No one got airborne for another couple of hours.

Jack