Aiming for maximum distances is not the best strategy for profitability. If you do the math, you'll see that the shortest distances yield the highest profit per minute than the longer ones do. While it may take more short flights to make the same profit as a much longer flight, you can do it in much less time, making short flights more profitable. Once you're done for the day, then you can send all your planes on a long trip so that you'll have a nice gain when you pick up the game again.
To do the test, fill up a plane with passengers/cargo for a long trip, and then take your profit and divide it by the minutes for the flight. Then do the same for a very short flight. You will see that the short flight has a much higher profit per minute than the long flight.