An answer on travel.se suggests that some pilots are smoking on long-distance passenger flights.
Can passenger airliner pilots smoke if both the captain and first officer agree it’s ok? If I recall, smoking is only prohibited on flights that require cabin crew as a crew health issue (sidestream smoke) and not as flight safety issue. Given that cabin crew are not on the flight deck, is there anything that prevents a pilot on a larger airline from lighting up?
For the purposes of the question, let’s consider flights originating in USA, EU, UAE, and China as the four biggest country/areas.