Originally Posted by
Beltway2A
As others have noted, fare rules most likely won't allow routing through Japan for those routes. For TPE in particular though, TPE-FRA is around 4 miles shorter than NRT-FRA. I don't disagree that JAL offers one of the best Y products out there, but you'd be adding an extra 1300 or so miles to your journey in the opposite direction to get it.
only china airlines offer the nonstop. i can think of many reasons why one would be looking for an alternative
btw, whist the great circle distance is 4mi shorter, tpefra avoids entering china so has a detour (tpefra block time is 90 mins longer than nrt fra)