Topline Shares of Southwest Airlines rose 9% on Monday and headed toward their largest single-day gain in nearly four years, after activist firm Elliott Investment Management announced a nearly $2 billion stake in the company and called to oust the airline’s chief executive and board chair. Southwest operates under “poor leadership” and a business strategy that “no longer succeeds in the ... [+] modern airline industry,” the activist fund said. Newsday via Getty Images Key Facts Southwest shares rose to$30 ...