789定位上係long range,實際上最長果十幾條航線一半都係789,不過339其實都係market 做long range,但係兩個都有好多medium haul。
而78X 就算冇IGW (暫時未見到type rating 有260t MTOW,)long haul 其實都冇問題,之前simple flyer ig 有個po 講78X最長幾條航線LAX-HND, AMS-LAX, EWR-TLV, TPE-SEA, ORD-HND係可以過萬km
所以789 又好78X都叫做可以fit 到CX 嘅need,可能789 long and skinny 好啲啲容易fill又飛到HKG-美國東岸,78X short haul 就效率高啲啲咁,但係咁細分別外人真係冇乜可能做到好嘅估計
另外789 78X commonality 有成95%,國泰兩樣都要又唔係話冇可能
AF 個 low J 359 用稍為high density 嘅 Safran Optima

叫做cheat 咗少少,如果用差唔多density cabin 嘅話:
Vietnam 359: C29W36Y240 789: C28W35Y211
China Eastern 359: C40W32Y216 789: C30W28Y227
Qatar 359: C36Y247, 789: C30Y281
分別係有不過好似冇咁大,好多時差一級嘅飛機座位數差40-60個(e.g. 359 vs 35J see CX/QR, 789 vs 78J see Eva Air),可以話359/789 其實都係半級左右

LH 359 就連PE 都一樣係2-3-2,不過有F好難比: F3C38W24Y201 789: C28W28Y231