According to one rant on the news, it seems airliners have suddenly taken over from diesel cars as causing the worst pollution.
CO2 emissions from the Q400 are better per passenger km than a car with only one person in, and only marginally more than diesel trains, and it's usually a shorter distance, but facts seem to be somewhat lacking in some of these arguments.
Diesel cars are better per passenger km then Q400 with only one passenger in. What a comparison in the quote above...