I flew BKK-PVG-JFK-vv twice this year in J. Seven out of eight flights had cigarette smoke wafting from the cockpit into the cabin. They smoke in there. And they open the door frequently enough that it gets out into the cabin. It's a very real problem. Only way to avoid it is to sit far enough back in the big J cabin on the 77W. If this bothers you, don't fly MU.