Agree with Elzilcho,
The smart Airlines dont run a seperate LCC, and incur all the duplication.
EG Cathay Pacific have long said they will not run an LCC, they regard the back end of their A330s as their low cost airline!
Likewise the big American carriers have tried the seperate LCC model, eg United with TED, Delta with Song, and wound them up, now they operate just the mailine operation, the domestic USA version of which is like a low cost anyway.
SAS also tried the seperate LCC, Snowflake, wound that up, and they now run their domestic and regional operations as a dual full service/LCC on the one Aircraft.
They have Economy plus for full flexible Economy fares, and these passengers get all the normal frills.
The back end is called Economy, you get one freee checked bag and free tea and coffee, but pay for anything else.
The big advantage for all these airlines, is that as well as no duplication in management,Aocs, Aircraft types, they can run more frequency under their own brand in any market they serve, than if they were operating 2 brands in the one market!
So for example if Qantas restricted Jetstar to leisure routes, and took them off the primary routes, the Qantas group could then increase frequency on these routes, to better compete with Virgin Australia.
Jetstar operate 3 times daily Melbourne to Perth, those 3 A320 flights could be replaced by 2 Qantas A330s or 3 737s daily, maintaining the Qantas Group capacity on that route, but giving the high yielding passengers more Qantas frequency!