Exeng, the carriers saved money on more than just maintenance. Back in the 80s the airlines in Canada were given the green light to cut the amount of fresh air coming into the cabin in exchange for the smoking ban, so now cabin air quality is worse than it was when smoking was allowed. Forget the propaganda about HEPA filters for the recirc air- they do nothing about CO2 and only trap a minute portion of the microbes floating around. As a scientist who contributes to another forum wisely says, the solution to pollution is dilution.
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Nuke the rainforest- it's more efficient than logging.