With this the number of airfields open to civil aircraft in the archipelago to three, state-run Xinhua news agency reported.
The flight tests were held after a tribunal formed by the Permanent Court of Arbitration, (PCA) hearing a petition from the Philippines quashed China's claims of historic rights over South China Sea.
Besides the Philippines, Vietnam, Malaysia, Brunei and Taiwan challenged China's claims.
China which has boycotted the tribunal has rejected the verdict saying it is null and void.
The two flights, an Airbus A319 chartered by China Southern Airlines and a Boeing 737 by Hainan Airlines, both returned to Haikou after a short stay on the reefs.
The round trips came one day after a Cessna CE-680 flew to the two reefs to ensure that both airfields are prepared for civil flights.
