According to local news, the labor action began as of 0600 local time.
https://www.scmp.com/news/china/soci...china-airlines
Among the things the union is seeking:
3 pilot crews on flights over 8 hours, and 4 pilots if over 12 hours.
Transparent upgrade selection process based on seniority and hours flown instead of company discretion
End company harassment of pilots involved in union activities
Stopping the practice of hiring foreign pilots during times when the Company is not hiring locals.