 China Southern Airlines on Tuesday rolled out an all you can fly pass, becoming the latest in a fleet of cash-strapped carriers to join a promotional craze that analysts say has helped revive a coronavirus-ravaged air travel market. At least eight of Chinas dozens of airlines have introduced similar deals since June, often priced around 500 for in some cases unlimited flights. The global aviation industry is keenly eyeing China as a pilot for air travel recovery trends, as the country reopened its economy months earlier than other places after managing to bring the pandemic mostly under control - at least for now. 