From Mangalore to Sanya, only connecting flights with two transfers are available. If you’d like to take Indian Airlines, you could transfer at Delhi and Guangzhou. From Bangalore to sanya, there are conjoint flights both with one or two transfers. However, Indian airline is not operating on the route. It takes shorter flight time from Bangalore to Sanya. For the cheaper tickets, you could consult some local booking agencies where more preferential international tickets maybe on sale.