I think I haven't made my point clearly, so I will reiterate: There are only some few tens of thousands of airplanes on this planet, compared to billions and billions of automobiles, trucks, diesel locomotives and backyard lawnmowers (etc) ALL of which (A) burn petro fuels and, (B) operate at the surface, where their emissions are far more prevalent.good so we agree it's bad pollution
Further to the other point (RE: contrails). It would certainly be possible to eliminate the formation of visible aircraft-produced contrails (which are, ultimately, merely a type of cirrus cloud) .... this would be extremely expensive and inconvenient, though. Would require the extra expenditure of fuel burned...which would then INCREASE the amount of pollution emitted! And all of that pollution in form of water vapor would by its very nature, as water vapor, be invisible to the Human eye.