Activist investor Elliott Management is preparing to launch a proxy fight at Southwest Airlines, and intends to nominate as many as 10 directors to the company's 15-person board, according to a person familiar with the matter.Elliott plans to call a special meeting, rather than waiting for the company's annual shareholder meeting, the person said. Southwest's last shareholder meeting was held in May.The activist has already amassed an economic interest of roughly 11%, although only 7% is in common stock. El ...