Contrails have been around since World War II, when airplanes were able to fly high enough for exhaust water vapor to freeze into ice crystals. And the persistence of the trails was always a function of the altitude and humidity conditions at which they were formed, higher being more persistent. In the 1980s, airlines began to operate airliners that flew at higher altitudes, thus more persistence. They cross the sky...and they are meaningless. Eventually--like any other high altitude cloud--they will dilute with the air and dissipate. Consider that the only reason you can see them is because they are brighter than the sky background. The idea that they are blocking sunlight is facetious. People must not have any experience of cumulus clouds. (I live in the Pacific Northwest, and pervasive overcast is a frequent fact of life. It only dims the sunlight slightly. We have no problem growing crops and exceedingly thick forests, and getting suntans.) I live under an approach/departure corridor for Seattle-Tacoma International airport and see contrails all the time. They are a nothingburger. No one gives them a second thought. In my long life (3/4 of a century), they have never been a popular subject of concern. (We are more concerned about the prospect of rainfall.) They impair nothing.

As for the chemicals, good luck proving they come from airplane exhaust. Jet fuel is rigorously formulated to preclude metals, which can gum up turbines with slag. Some of the elements mentioned in the complaint are common in brake linings, and the dust from brake wear can easily be windborne away from roadways. Dust from many states away can commonly be carried westward on the prevailing winds (e.g., the Oklahoma Dust Bowl erosion). Other mineral elements are consistent with the approximately 50 tons/day of meteoric matter drifting down on us---which no one mentions. (It is true that the internal components of turbine engines and fuel feed systems can result in transition metals chemically interacting with fuel, a condition which is known to be adverse to engine performance and is prevented as much as possible. A reference on this point is available at https://www.sciencedirect.com/science/article/abs/pii/S0016236125023981.)

Much noise has been made about the few cases where state governments have outlawed this supposed aerial pollution. Contrails continue. No airline will ever be convicted of pollution from generating ice crystals, since it is chemically impossible to combust hydrocarbons without generating water vapor (and thus form contrails).

The one good thing about this latest approach is that they had the wisdom to distance themselves from Dane Wiggington, who profoundly does not know what he is talking about.