July 1987 -- This small tornado was photographed from inside a plane on the runway of (the now defunct) Stapleton Airport in Denver. It would probably be classified as an F1, and didn't appear to be a threat, so nobody panicked even though the plane was stuck in the queue on the runway for more than an hour, due to the weather. Before forming into a tornado it looked like swirling smoke on the ground, and didn't really register with anyone until we came into view again and saw that it had "filled in". When we finally took off, the plane hit strong turbulence not too long afterwards. But we arrived safely home, 2 hrs 45 minutes late.