“One curious and unintended consequence of the aeroplane ban [on smoking] was that airlines began to save money by changing the air in the cabin less frequently. Traditionally, this was done every two minutes and old air was never recirculated, but with no tobacco smoke to draw attention to the quality of air, the carriers reduced air changes to once every twenty minutes. This led to a musty aroma on board and, according to a report in The Lancet, contributed to the appearance of Deep Vein Thrombosis, a disease unknown in airline passengers until the 1990s.”
Page 163 of Velvet Glove, Iron Fist: A history of anti-smoking. By Christopher Snowdon.
Entirely selfishly, I am delighted that I travel in a smoke-free airline industry, although it is a shame that this change came about through the coercion of the state and not in reaction to consumer choice via a market. After all, there are many irritations involved in flying that might be amenable to a market solution, if it was available, such as screaming young children or patronising and idiotic flight attendants.