An American Airlines Airbus A321 taxis at San Diego International Airport as a United Airlines airplane departs on Aug. 24, 2024 in San Diego, California. Kevin Carter | Getty Images News | Getty Images The head of American Airlines ' pilots union told members that  United Airlines  CEO Scott Kirby's merger idea showed the kind of "bold vision" the carrier needs, even as the union stopped short of endorsing a tie-up between the two airlines. In an email to pilots on Monday, seen by Reuters, Allied Pilots Association President Nick Silva said Kirby's vision could be "transformative" for passengers, communities and American Airlines pilots. Silva's message shows how Kirby's rejected proposal has become a new pressure point inside American. APA is not backing a merger, but its president is using the idea to argue that American needs a more ambitious strategy and stronger leadership to close the gap with rivals.…