this game is also about cash flow. So if you have $10M in the bank, don't spend $10M on new leases. You'll need money for slots, and to cover losses whilst routes build up.
It's also better when an airline is new and cash is critical to do lots of short routes, 3 or 4 a day, rather than 2 long routes. You get more $/hour in. And as others have said scheduling, make those planes work. If you get somebody that lands way from base at 23:55 that's ok, hold it until 5am and have it return. And if you can use timezones to make this even more efficient, all the better.
And small planes - yep it's going to be hard as slot costs are slot costs whether it's a Jumbo or a Piper Cherokee. Also don't start in an airport that's full of competitors, or even one good competitor. To see if another player is good, click on airline CEO username and look at their achievements.
A mentor is a good idea, the game's not that hard once you get past the starting oopsies.
Simon