AMR Corp. Chief Executive Tom Horton is in talks about becoming board chairman if the American Airlines parent merges with US Airways Group Inc., one of a number of signs both companies are nearing a deal that could create the world's largest airline by traffic, the Wall Street Journal reported today. The negotiations are fluid and might not result in Horton's assuming that role, as he could become a vice chairman, senior adviser, take on another role or choose to retire. Horton's future is being debated by AMR creditors and others because Doug Parker, US Airways' chairman and chief executive, is widely seen as the person who would run the combined airline as CEO. US Airways, in a November merger offer, proposed Parker assume the chief executive and chairman posts in a combined airline.