Interesting insights, highly appreciated!
Please allow some questions/comments:
1) Regarding props/jets: I see that jets are faster and thus need less staff and less aircrafts in total which saves costs. Still, fuel consumption would still be higher (around 30%). 2 Viscounts need ~1800kg/h, 1 DC9 needs ~3000kg/h. So I think the difference would not be that much. Yes, I need more staff and maintenance, but I also save some fuel. The main problem is the demand, which is mostly around 50-70. Jet's still do not make sense for many routes I am flying (either too big or too short range). Where possible, I am using DC9 instead of Viscounts (e.g. when demand increases or competition is gone). I'll use Q400 or Dash8 later on to save some more costs (e.g. 2 pilots, more speed, less fuel).
2) Oversupply: I am not sure which oversupply you'd mean. Except for a few exceptions (e.g. Istanbul), I am always trying to fulfill the exact demand (not caring for competition). So if a route has 120 demand, I schedule 2 Viscounts at 59 seats each. Or 2 DC-9-21 for a route of 140 demand etc. I prefer Viscounts on routes where competition is tough to have a higher market share through higher frequency (e.g. 4 Viscounts for 200 demand instead of 2x DC-9-34).
3) Scheduling: I have a fleet utilization of 16.2h which is pretty good I think. Especially the Viscounts have a high utilization as they fly day/night (thanks for their low speed). I let them fly from 22:00 local time to the middle east or UK where they arrive at 06:00. DC-9 are faster and cannot have night flights unfortunately without having bad arr/dep times.
4) Level 3 bases: Please correct me if I'm wrong, but I cannot operate DC9 from level 2 bases. And those DC9 are my most profitable aircrafts. I see that BACs are considered "Medium" aircraft. But the range is not sufficient enough for my needs (2000NM). Would be a different story if I were in the heart of Europe, but Greece is quite in the middle between Europe/Middle East and I need medium haul for either direction. So unfortunately I cannot save costs by shrinking the base sizes either.