How have deep-seated cultural human factors (particularly in east Asia) in the cockpit been successfully managed in the past 20 years?
The commercial aviation world today emphasizes crew resource management (CRM) as an integral part of flying. The premise of effective CRM lies in the principle that any member of the flight crew, whether it's the captain or the first officer, is able to, and should express honest and valid concerns during the flight without worrying about being marginalized or ignored.

Before I start, I would like to point out that Asian airlines are not the only ones to exhibit poor crew management in the past. KLM 4805 (Tenerife), Eastern 401 (crew gets distracted on approach trying to replace a light bulb), and more recently, Air France 447 serve as some examples.

I think the reason why crew management-related accidents in Asia come under the spotlight much more than others (I still hear Asiana 214 jokes all the time, and it's getting really old...) is the fact that the very nature of East Asian culture counters the basic premise of effective CRM — that regardless of position or status in the cockpit, each crew member has a responsibility and a right to speak up. Instead, everybody has a clear-cut hierarchical position roughly based on age. Therefore, whereas accidents in the West are viewed as one-off mistakes made by individuals in an individual case, accidents in the East are viewed more as a natural consequence of the area's culture.

Now, Asian aviation has changed a lot since the '80s. CRM training is a big thing in the industry (just like how the western world has been doing it) and there has been a giant push in the general culture as a whole to create an environment where everyone is heard with equal weight. Change alright, but the roots of old culture remain despite these recent developments, and this is especially true in the corporate environment (including the cockpit). The give-it-to-me-straight-doc cockpit culture in the East still makes it very hard for the FO to speak up and sort of awkward for the captain to allow other crew members to cooperate, even if he or she is willing to make the most use of the crew body.

So, to wrap up my answer to the question, there have been numerous efforts to improve crew management/human factors in the East, but we haven't quite seen the full effects of such changes. Perhaps when the current generation of pilots go (most of them in their '40s and '50s, who were born before the rapid cultural changes in Asia) and the newer, younger generation sets in might we be able to better gage the true effects of changing culture in Asia.

There is no way to summarize this entire subject in a perfectly objective way and there will be people that disagree with some things I've noted. All my above observations were made as a Korean now living in the US. Hopefully my 2 cents help.