I am really concern to hear that some trying to argue that it is because of high demand that is why airlines provide such services. Thus, it should be a market failure due to over consumption of air travel by consumers. This argument is wrong fundamentally as the pollution is generated in the "PROCESS OF FLYING", which is similar to that of "PROCESS OF PRODUCING METALS'. So how can we say that pollution by factories in the process of production because of high demand for their products, it is not the fault of the factories but rather the consumer who "generated" the negative externalities?
It must be very clear that for over consumption that result in negative externalities must be resulted from the action of "direct consumption" from the consumers like in the case of road congestion and alcohol etc