my daughter and friend are flying from seattle wa to melbourne australia and fly to Shenzhen China with a 11 hour layover, they dont plan on leaving the airport. then they fly to Xiamen China also not leaving the airport this layover 13 hours.cant find out if they need a visa. orbits told them no, i keep reading things and im not sure. visa? transit visa?read where that was good only 24 hours or less and maybe only one stop . please any advice