(MENAFN - Asia Times)

China has allowed two-way traffic on a civil-aviation route that runs almost parallel to the centerline of the Taiwan Strait, the de facto sea and air border between the mainland and Taiwan.

China's Civil Aviation Administration said on Thursday that civilian planes heading north would now be allowed to use M503 – a route previously reserved for southbound planes only – in a bid to alleviate airspace congestion in southeastern China, notably for flights between hubs in the affluent Yangtze River Delta and the Pearl River Delta.

Taiwan's civil-aviation authority has lodged an official complaint to Beijing and to the International Civil Aviation Organization (ICAO).

Route M503 runs almost parallel with the centerline of the Taiwan Strait, where a new unilateral two-way traffic arrangement has been made by China. Photo: Central News Agency

Taiwan is concerned that Chinese reconnaissance and other warplanes disguised as passenger or cargo planes can now fly the route and 'unintentionally' veer off the course eastward to enter Taiwan's territorial airspace to get intelligence on airbases, defense deployment and infrastructure on the island's west coast.

Route M503 is just 7.8 kilometers from the strait's centerline at the closest point.

Observers say that even though bombers and spy planes from the People's Liberation Army have been frequenting peripheral airspace surrounding the island in weekly and even daily 'freedom of navigation' patrols, so far the Taiwan Strait has been off-limits.

'China must be held accountable for any serious consequences that would affect aviation safety and cross-Strait relations,' Katharine Chang, minister of Taiwan's Mainland Affairs Council (MAC), said at a news conference in Taipei.

‘Move breaches terms of 2015 agreement'

Beijing and Taipei inked an agreement in 2015 that only southbound flights would be permitted on Route M503.

The route was set within the Shanghai Flight Information Region instead of the Taipei region, and it maintains a safe distance from the Taipei region, Xinhua noted in a report back in 2015.

If flights have to deviate from the designated route because of inclement weather or for other reasons, the flights should move west into mainland airspace, according to the 2015 agreement.

But the deal three years ago was a contentious issue as many protested that it could endanger Taiwan's national safety.

Taiwan Civil Aeronautics Administration statistics show that about 60 to 70 flights use the southbound M503 route every day.

An airliner of China Airlines, Taiwan's flag carrier, is seen above the Taiwan Strait. Photo: Handout

Taiwan said it was not informed about the move until frontline aviation controllers in Fuzhou and Xiamen in the mainland province of Fujian told their Taiwanese counterparts on Thursday morning that planes could now fly both ways on Route M503.

'We believe that China not only breached terms of the 2015 agreement, but it is also attempting to cover its malicious intentions toward Taiwan – both politically and militarily – under the guise of civil aviation. The move has generated concerns that it could potentially change the 'status quo' across the Taiwan Strait,' Chang said.

Flights on the M503 route carry not only Taiwanese and mainland Chinese passengers but also people from other nations, and their safety could be affected by the unilateral two-way arrangement, the MAC minister said.

An official with Taiwan's civil aviation authority said: 'We have not negotiated over the issues involving northbound flights on the M503 route or the three extension routes, so we want [mainland China] to avoid using them. Otherwise, our air-traffic-control officers would not know how to guide the flights in emergency situations.'

Taiwan's Central News Agency also reported that an unnamed US State Department official had expressed concern that China 'has modified the use of civil aviation flight routes in the Taiwan Strait without consultation with Taiwan authorities,' and said any such issues should be 'decided through dialogue between both sides.'

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