(just read demo is only using Y-class. Well, following would work in real game)
If they have also C demand, then maybe. If you have a suitable plane (short turnaround time, small fuel consumption, suitable size)
Generally it is best to first take all longer routes with good C and F demand. And configure your planes to take max of those classes, they are the moneymakers.
Then you can use all shorter routes with C-demand to fill the schedules (planes don't make money when they stand at ground, so fly them as much as you can).
And only after that start filling short routes with just Y-class demand.