Claire,I guess the pollution might be interpreted in different ways. But in terms of greenhouse gases, cars are much more of a problem than planes, and are a big part of the overall problem, not at all 'minor'.I googled "CO2 emissions by sector".What I learnt is that CO2 emissions from road transport are about 5x that from aviation.Have a look at:ourworldindata.org.And to quote wikipedia:"Transport in the United Kingdom is the biggest emitter, being responsible for over a quarter of GhG.[1] This is mainly due to road vehicles, especially cars."
Simon Pedley ● 2012d