Airline within airline business model refer to building a low cost subsidiary by legacy, network and/or traditional airlines because of different purposes. In the literature, those airlines are named as airline within airline and this business model also named as airline within airlines model. Airline within airline business models and performance of this model are examined and discussed intensively. Researches about airline within airline business models in the literature emprically showed that airline within airlines are built as a response to low cost airlines' threat. In this study AnadoluJet which is only example of airline within airline in Turkey is examined as a case study. Research results showed that Turkish Airlines built AnadoluJet because of the threat of Pegasus Airlines and AnadoluJet is a competitive weapon of Turkish Airlines against the competition of Pegasus Airlines.