What is the basis of Southwest’s competitive advantage and the potential challenges to its strategy? What internal resources and assets does Southwest

Attached is the case study and case study questions.
Case study:
What is the basis of Southwest’s competitive advantage and the potential challenges to its strategy?
What internal resources and assets does Southwest have that may give it a competitive advantage?
Was Southwest growing big and ignoring the focus that made the airline so successful for so long? Why or why not?
Would the success continue under Kelly when the core elements of the company’s original strategy- low cost, organic and domestic point-to-point short-haul growth, and customer-centric culture- were simultaneously changing?
Was the low-cost business model (frequent takeoffs/landings/short flight times) creating more wear and tear on the planes and in turn, putting passengers at risk?
What prevents larger competitors, such as American, Delta, or United, from imitating Southwests approach? What prevents new entrants from successfully imitating Southwests approach?