You guys got me wondering about jet contrails so I looked it up. It appears that you can get a short jet contrail like that when conditions that allow the formation of contrails exist in only that part of the troposphere. That also accounts for intermittent jet contrails. It may also indicate that the jet forming the contrails is cruising at 30,000+ feet altitude. Yea, I know too much time on my hands.
Here comes my a little bit strange cloud picture. It shows Mt. Fuji, taken from Tokyo ( don't ask, how many mm telephoto ;D ). It has been taken a few seconds after the sun went down exactly in the center of the top, which makes the mountain look like it would burn