. . . is the latest recommendation from the British Medical Association (more details here). The proposal is justified on similar grounds to the ban on smoking in public (e.g., the potential harm to the health of other non-smokers). On the one hand, toxins related to smoking may be many times higher than a smoke-filled bar. On the other hand, there appears little consideration of the question of whether non-smoking passengers might consent to others smoking.
Whatever the general merits of the proposal, I suspect this recommendation will receive attention but not become law.