This is not only Vietnam's concern

InterAksyon.com
The online news portal of TV5

MANILA - China’s construction of an airstrip at Mabini Reef could be the first step in Beijing’s plan to establish an air defense identification zone (ADIZ) over the disputed Spratly Islands and the entire South China Sea.

This was the assessment of a top Aquino administration defense official, who has intimate knowledge of China’s recent activities in the disputed Spratly Islands. Both the Departments of Defense and Foreign Affairs confirmed there have been construction activities in Mabini Reef (internationally known as Johnson South Reef) but which China calls Chigua Reef.

Dr. Peter Paul Galvez, spokesman of the Department of National Defense, confirmed “ongoing reclamation or earthmoving activities” at Mabini Reef and noted the dimensions of the construction area are consistent with that of an airstrip. 

“If indeed this is an airstrip, then definitely it will be of great security concern,” the defense official warned. When asked if it could be the start of Beijing’s plan to put up an air defense zone over the South China Sea, the official replied: “Possible.”

In late 2013, Beijing announced it was enforcing an air defense zone over the East China Sea, which covers a group of islands disputed by China and Japan.  Last Febraury, the Japanese newspaper Asahi Shimbun warned China was planning an air defense identification zone for the South China Sea as well.

Under the ADIZ, all foreign aircraft are required to report their movements to China.
The United States warned China against considering any South China Sea ADIZ plan. China denied it had such a plan.

First air strip, but 6 garrisons so far

But if the construction activities at Mabini Reef are confirmed to be an airstrip, this would be the first one built by China on any of the eight reefs and islands it occupies in the Spratlys.

Apart from the Philippines and China, Brunei, Malaysia, Taiwan and Vietnam have their own claims in the Spratlys – which is widely believed to hold vast reserves of oil and gas and is also known as a prime fishing area.

As far back as 2001, China has been aggressively building up its armed garrisons and facilities in six islands and reefs located well inside the Philippine territory of the Spratlys.

China has gradually built up its garrisons at the Kagitingan Reef (Fiery Cross Reef), Calderon Reef (Cuarteron Reef), Zamora Reef (Subi Reef). Gaven Reef, Mabini Reef (Chigua Reef) and Panganiban Reef (Mischief Reef).