On what basis do you get the "greatest sustained business performances of the last 50 years", let alone within the airline industry? Especially since Walsh has not been CEO for 50 years.
I draw your attention to this stock price chart, where Air Canada is the dark blue ( mostly top line) and IAG is the light blue. Who has given a better return to the shareholders? That is the job of a CEO after all. I'd venture that Calin Rovinescu is a much more successful airline CEO than Walsh.