1. How can airplane contrail (man made) be natural?
2. How can you compare "natural" with "unnatural" if you have no point of reference?
3. Do you have any documentation of experiments with water vapor and chemical vapor to make valid comparisons?
4. Did it ever occur to you that airplanes fly at different altitudes and as such leave different trails? Depending on currents, layer temperatures and vapor densities, number of engines on the plane (more engines = more vapor created)? Same old song and dance !