Schedule problems

I have created a flight schedule to an airport and the return flight and the boxes stay red but the schedule icon on fleet management is green?

The icon in the fleet management page just shows whether you have activated the flight schedule or not. If there is no flight schedule, then it's red, if there is a flight schedule that has not been activated yet, then it's yellow and if there is an activated flight schedule, then it's green.

So in order to see whether your flight schedule actually works or not, you have to rely on the coloring of the flight schedule page. If it is red, then you should check that schedule once again!