Air Defence Identification Zone
The Air Defense Identification Zone is airspace over land or water in which the ready identification, location, and control of civil aircraft over land or water is required in the interest of national security. China's Defence Ministry announced its ADIZ over a vast area in the East China Sea on November 23, 2013, which covers the area around the Diaoyu islands, controlled by Japan and known as the Senkaku Islands. The establishment of this zone drew strong opposition from Japan, the US and South Korea, becoming a flashpoint in East Asian politics and security.
China ‘monitored’ US bombers as they flew over air defence identification zone
Ministry says it observed 'the whole process' as American planes flew across newly declared defence zone in defiance of notice requirement
Chow Chung-yan and Kristine Kwok
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The Ministry of National Defence said yesterday it "monitored the whole process" as two US bombers flew across the country's newly declared air defence identification zone (ADIZ) over the East China Sea without notice.
The statement came after what was seen as a deliberate gesture by the Americans late on Tuesday to defy a Chinese declaration that requires foreign aircraft to give notice before entering the area. The US Air Force flew two B-52 bombers through the zone on a return trip from the US territory of Guam.
Defence ministry spokesman Geng Yansheng said the military was able to identify and monitor the US aircraft during their transit across the zone.
"What we want to stress is, the Chinese side will monitor the activities of any flying object in the Chinese ADIZ," Geng said. "The Chinese side has the capabilities to exercise effective control."
Watch: The South China Sea diplomatic row intensifies
Experts said this may set a future pattern, with the US testing Chinese resolve and handling of its new rules and China demonstrating its determination and capabilities without directly confronting the Americans.
"What we see today may happen again," said Richard Hu, an international expert at the University of Hong Kong.
"It will be a process of probing and testing from both sides. Eventually they will come to a tacit understanding. But China will never abolish the zone. It has all the legal ground to do so. Other countries will have to accept it as a political reality."
Hu said the US would continue to probe and test China to find out its bottom line and capabilities in keeping the new rules. China's declaration last Saturday triggered fierce protests from other countries, particularly Japan and the US.
Chinese experts argue that China is the last major power in the region to establish an ADIZ - after Japan, South Korea, Vietnam and even Taiwan.
In 2010, Japan expanded its own ADIZ in the East China Sea by 22 kilometres to cover Yonaguni Island. The expansion led to an overlapping with Taiwan's ADIZ and Taipei at the time expressed "regret" to Tokyo.
Di Dongsheng, deputy director of the Centre for China's Foreign Strategy Studies at Renmin University, said creation of the Chinese zone was largely a response to Tokyo's move in 2010.
"It is not a provocative gesture. It is a response," Di said. "How can Tokyo and Washington criticise us when what we are doing is just following their examples?"
A US diplomat said Washington and its allies were concerned by ambiguities in the Chinese declaration and how Beijing interpreted international law, which promises freedom of navigation for foreign vessels and aircraft when they travel across another country's exclusive economic and air defence identification zones.
A foreign plane needs only to notify the relevant country if it intends to enter into its sovereign airspace or territorial waters. Lacking detailed operational instruction, the Chinese declaration seems to suggest that Beijing would require all aircraft - regardless of their final destination - to give prior notice.
The flight of the US bombers was intended to challenge the point and proves to Beijing that the US will not relinquish the free navigation of its aircraft.
"It is understandable why the US reacted this way," Di said. "The US - the US military in particular - has to protect its credibility before its allies. But in the long run, this will only play into China's hands.
"What the US is doing is going to set an example for China to follow. In future, China can have military aircraft transit across other countries' ADIZ on the grounds of innocent passage. It will be hard for the US and Japan to criticise China because [Washington] set the precedent."
Hu said the development may be similar to what happened between the Chinese and US navies after China introduced the exclusive economic zone in the South China Sea in 1998.
Chinese and American vessels clashed on numerous occasions because of their different understanding of innocent passage under the international law.
By establishing the airspace defence zone, China is not making any further claim to its sovereign airspace, mainland experts say. It is simply asserting its rights to monitor and police airspace near its sovereign territories.
"These are two completely different concepts," military law expert Chai Lidan was quoted by Xinhua as saying yesterday.
"A country enjoys complete and exclusive rights in its sovereign airspace. It has the right to intercept, repel or even destroy unauthorised foreign aircraft entering into that airspace.
"But for the identification zone, it only has the right to track, identify and manage foreign flying objects," Chai said. "It can only give warning and make interception if it believes the foreign aircraft has hostile intentions."
All experts agreed that China needed to further clarify its declaration and issue more detailed operational instructions. This would take the guesswork out and reduce risks, they say.
"[The defence ministry needs] to give a full explanation of what they consider a threat and how they will respond to a threat," said Liu Jiangyong, a Japan expert at Tsinghua University.
Di, Liu and Hu all believed the issue would dominate the talks when US Vice-President Joe Biden visits China next month.
Watch: The South China Sea dispute explained