BBC Horizon propaganda program (about 2007) investigates "global dimming" and proves that it's caused by clouds. It starts by noting that airplane vapor trails create clouds and cause dimming but quickly switches to blaming it on human-created smoke pollution.
Then it goes on to say that "dimming" has been protecting us from "global warming".
Then it switches back to airplane contrails, which stopped for three days after 9/11. So global dimming is caused by contrails, not human smoke pollution. Or both. And dimming causes death so we need to stop it. But global warming is bad. (Confused yet?)
Therefore we need to put up MORE airplanes to spray, erm, contrails. This will protect us from "global warming" which is caused by <cough the sun cough> CO2.
Note: please download and archive. This is a quicktime movie so it might need to be converted to play on your device.