here's what you do: if there is demand from airport XYZ to ABC (eg. EWR to CLT) of 150pax/day and you can fly that route with any aircraft from your fleet: choose the one closest to the demand (which would probably be the 737 in your case) and fly it there DAILY. then find another one and do the same until you have a relatively full schedule. Oh, and try to leave something like one hour between flights, it saves your @ss when the first flight is delayed an hour or so, so your new flight only departs 5-10 minutes late rather than 60-75 minutes late. And leave a long turnaround inbetween arrival and departure at your destination airport; again it saves your @ss when a flight is late.
basically just do that until all your planes are full with routes that are more demanding than the capacity of the AC, and you should see the money come through your doors in truckloads.
maintenance should be conducted on SAT or SUN, as your weekdays are the most demanding. (B-checks just put on a SAT and leave it, A-checks should have a lot of room [preferably an hour on either side] so that there is no delays for departure because of maintenance issues prior to departure. If you can, get rid of the smaller plane (Aerospatiale) and the DC-9 and replace them with a Fokker Mk. 500 and a 737 respectfully. save you a whole lot of money on maintenance, training costs and fleet commonality.