Probably using 7-day scheduling. Use 7 aircraft of the same type flying a weekly schedule of say 4 to 6 flights (depending on length). Each aircraft is then 1 day out of sync. The net effect is that each route is flown once each day (although of course it can be more than that if the schedule for the first aircraft flies to the same place more than once in its week voyage).
You can do the same with s/h flights, with say 18 flights per week for the rota.