Wednesday's test flights followed one over the weekend that marked the first trip to Fiery Cross Reef, which brought a protest from fellow claimant Vietnam.
China's creation of seven new islands by piling sand on reefs and atolls has been condemned by its neighbors and the United States, who say China is raising tensions in an area where six governments share overlapping maritime territorial claims.
The U.S. State Department responded to Saturday's flight by reiterating calls for a halt to land reclamation and militarization of outposts in those waters.
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