As I do not want to have Turboprops in my main fleet as I want to keep it with 3 types (EMB, A319/320 and 787)
Would my subsidiary interline with me automatically or would I basically need to start from scratch even though they would be operating similar routes (but with less demand) ?
Or shall I just bit the bullet and get some turboprops? (even though this will increase my maintenance costs significantly)
You send an IL request to your parent airline, just like you would with another player
Lots of players use this strategy to keep costs in their mainline down. Also the main airline can have all the IL’s with dozens of players, whereby the subsidiary can just be with your main airline, so the only connections are going to your own airline, and it also keeps costs down on the Sub as well
With turboprops I always put them in a subsidiary because they have a negative impact on image. Otherwise it’s always up to the whichever option it’s the cheapest and most convenient is the best. Separating A320s and 737s into different companies might be smart from a cost perspective but if you have a lot of them and they operate in the same markets it will usually be a management nightmare so it’s easier to keep them together even you will pay more.