LAST year, Bob Fornaro, the boss of Spirit Airlines, talked of the effort his firm had made to reduce the number of customer complaints. The ultra-low-cost carrier, dubbed the most hated airline in America by Bloomberg, had long been ranked as a primary purveyor of passenger pain, regularly propping up lists that rate airline service. Alas, Mr Fornaro’s efforts seem to have gone unrewarded. Complaints per passenger remain easily the highest of any of the big American operators. In fact, as our chart shows, things seem to be getting worse.