In 2008-2010 I was playing this game, so I used to do these 2 features:
1) Take as many planes as you can, only then buy SLOTS, because with slots you can go into MINUS. If I dont, someoneesle will
2) Take the rout with most Firs Class, like Dubai - Taiwan (dont remember airport there), Take pure luxury 747-400, and dig gold.
On thsi route I had 1 747-400 full of First Class, and 5 747-400 pure Business Class )))
I finished that game 10th if not mistaken )))
immeditaley i did it, this feature was deleted, so Half of pax had to be poor economy passengers.