Research DesignThe case study approach is widely used in business and management research (Eisenhardt and Graebner 2007). Case study research is concerned with the complexity and particular nature of the case in question (Stake, 1995). The essence of case study research is to collect a holistic view of a phenomenon (Yin, 2009). The case study focuses on the examination of characteristic, functioning part, and the structure. A case can be a location, organization, person or event. The most common term related with the case would be a location such as a workplace or organization (Bryman & Bell, 2011). The objectives of this research are to analyze the influencing the decline of the airline’s financial performance of Thai Airways. Thus, a case study will be a suiting research design as I will be able to have a comprehension of an organization regarding the financial performance and its influencing. A longitudinal case is related to the change of situation over time (Bryman & Bell, 2011). A longitudinal case study, therefore, will be a suiting type of case study as the aim is to describe and explain how and what factors influence financial performance of Thai Airways during 2013 to 2016.Data Collection MethodThis study utilized both primary and secondary data. Primary data is collected from Thai Airways official website, press releases, annual and financial reports. Secondary data is collected via reliable public resources: international aviation associations such (IATA and CAPA), news resource (Bangkok Posts, Reuters, etc.), published articles and journals by universities, institutions, accounting firms and research portals. Analysis    The analysis process of this thesis will follow an inductive method. With an inductive method, the outcome of the research is a theory (Bryman & Bell, 2011). Thai Airways’ data on strategies, the business model, will be examined and compared with Qantas Airlines to discover the common factors leading to airline’s financial decline.