More specifically, Berkshire Hathaway was the largest shareholder of Southwest Airlines Co. (NYSE:LUV), with a stake worth $3500.2 million reported as of the end of September. Trailing Berkshire Hathaway was PAR Capital Management, which amassed a stake valued at $304 million. AQR Capital Management, Two Sigma Advisors, and Citadel Investment Group were also very fond of the stock, giving the stock large weights in their portfolios.