[BenLurkin]

Since man has flown above a certain altitude, yes.

Hard to see how people can’t know something that basic.

[MeanWestTexan]

“Hard to see how people can’t know something that basic.”

I am increasingly not amazed at the lack of scientific understanding of people. I used to be upset, and now I sit back and know knowledge is power.

[IYAS9YAS]

Since man has flown above a certain altitude, yes. Hard to see how people can’t know something that basic.

Actually, depending on speed and humidity, you can get the same effect at ground, or close to ground level. High-speed racing with spoilers will show contrails coming off the car, also, the old aircraft pics above show the props creating it at low altitude.