American and United aircraft meet at Miami International Airport in May. (Photo by Jakub Porzycki) NurPhoto via Getty ImagesEven before Monday’s stock market rout, airline shares were having a bad year. Among major carriers, American was having the worst year of all, while United was gaining support from a leading market strategist who now views the Chicago-based carrier as the industry leader.“Surprisingly, American has led on the downside,” Stephanie Link, chief investment strategist and portfolio manager ...