BEIJING: China is building a third aircraft carrier based on American models as it seeks to fortify its claims in the disputed South China Sea and dominate the larger Indian Ocean region to realise its blue water aspirations.Chinese experts said China is on course to build 5-6 aircraft carriers.While the first aircraft carrier, Liaoning , is a refitted Soviet-era ship, the second is being built on the same model with more advanced facilities and is likely to enter service in 2020.The latest carrier, under construction at Shanghai, is based on US models, state-run Global Times reported today.Based on information released by Chinese defence ministry, the second Type 001A carrier being built at the northeast Dalian port uses the ski-jump technology for aircraft to take off, like the first carrier Liaoning rather than a more advanced catapult technology used by American carriers.The second aircraft carrier is expected to have a displacement of 50,000 tonnes.China is looking into catapult technology for the third Type 002 carrier being built in Shanghai, the daily quoted Li Jie, a naval military expert, as saying."In other words, 002 is entirely different from Liaoning (001) and 001A, and it will look like a US aircraft carrier rather than a Russian one," Li added.Official Chinese media have earlier reported about the possibility of a third carrier but it is the first time they have announced that it was being built.Most advanced carriers use the Electromagnetic Catapult System, or Electromagnetic launcher (EML), to launch fighter jets, but China is also testing steam catapults, Li said."In order to protect China's territories and overseas interests, China needs two carrier strike groups in the West Pacific Ocean and two in the Indian Ocean . So we need at least five to six aircraft carriers," Yin Zhuo, a senior researcher at the PLA Navy Equipment Research Centre, said.Chinese media has often highlighted the construction of aircraft carriers as the US deployed aircraft carriers in the disputed South China Sea challenging Beijing's claims.The US Navy on Sunday announced that an aircraft carrier strike group has begun "routine operations" in the South China Sea. The announcement came despite a warning from China not to interfere with Chinese sovereignty in the region.China has a long history of maritime disputes with its South China Sea neighbours. It claims almost all of the South China Sea, despite objections from the Philippines, Malaysia, Brunei and Vietnam.China has also created artificial islands in the area , outfitting some of them with military features.