A people of a Hong Kong-based aviation newsgroup (news://news.hkteen.org/hkteen.talk.aviation) said China Airlines cannot use polar routes on Taiwan - North America flights, because the polar routes have to go via Mainland China.

If the aircrafts of Taiwanese airlines (China Airlines and EVA Air) cannot fly over the air over Mainalnd China, then what is the routing of their westbound flights, like flights to Europe, Southern Asia? Do these flights fly over Mainland China? Do the flights to Europe fly northward over Russia? Or southward over Indo-China Peninsula and Southern Asia?

Thanks.