The route is just west of the strait median line – a notional midway point between self-governed Taiwan and mainland China.
The CAAC said it would also start eastbound operations of two side routes – W122 and W123 – which connect M503 with the cities of Fuzhou and Xiamen in Fujian province. All of the affected routes are within the Shanghai Flight Information Region.
The CAAC announcement comes just weeks after Taiwanese voters elected Vice-President William Lai Ching-te of the Democratic Progressive Party (DPP) as the island’s next leader.
Beijing, which sees Taiwan as part of China to be reunited by force if necessary, has described Lai as an “obstinate separatist” and warned he would bring the risk of war to Taiwan.
Most countries, including the US – the island’s informal ally and biggest arms supplier – do not recognise Taiwan as an independent state but are opposed to any unilateral change to the status quo.
Beijing’s Taiwan Affairs Office (TAO), which handles cross-strait matters, described the route changes as “routine operations” to alleviate pressure on flights, ensure flight safety and meet the region’s growing air transport needs.
It said the changes were “conducive to improving cross-strait flight operations and further facilitating people-to-people exchanges across the strait, which are in the common interests of compatriots on both sides of the Taiwan Strait”.
The Taiwanese Civil Aviation Administration (CAA) expressed “deep regret” and a “strong protest” over what it described as Beijing’s “unilateral adjustment”.
“The [CAAC’s latest] measure blatantly contradicts the outcome of the communication between the two sides in 2015 over the launch of the M503 route,” it said shortly after the announcement from Beijing.
The CAA added that it would work with the relevant authorities to assess and make public the potential impacts of the changes on both Taiwan and international flight operations.
The island’s defence and foreign ministries and Mainland Affairs Council also condemned Beijing on Wednesday over its move.
Beijing’s unilateral announcement in 2015 of the M503 route – which skirts the Taipei flight information region – had triggered grave concerns in Taiwan about safety and the integrity of its flight paths.
Beijing later agreed to move it six nautical miles (11km) to the west of the planned path, to reduce the chances of air traffic hazards in the busy Shanghai and Taipei flight information regions which are in close proximity.
Observers said the cancellation of the six nautical mile “offset measure” signalled that Beijing was trying to squeeze further into Taiwanese airspace, to facilitate warplane crossovers in any future conflict.
Chieh Chung, a senior analyst at the National Policy Foundation, a think tank affiliated with Taiwan’s main opposition party Kuomintang, noted that the M503 route is just 7.8km (5 miles) from the median line at its closest point.
“It will also cut short the air force’s response time should the People’s Liberation Army (PLA) launch an air attack on Taiwan.”
The change would mean the island’s defence forces would have to be “on constant alert, to monitor and respond to any crossovers from the mainland”, Chieh said. “It would also further exhaust our air force pilots and increase the chance of unintended incidents.”
Shen Ming-shih, director of the Institute for National Defence and Security Research, a government think tank in Taipei, said coupled with the PLA’s warplane sorties across the median line from time to time, “the civilian mainland planes’ crossovers would serve only to obscure the existence of the median line further”.
In Taiwan election wake, PLA resumes regular military activities near island
In Taiwan election wake, PLA resumes regular military activities near island
In recent years, the PLA has increased the number of warplanes crossing the media line, denying that the unofficial barrier exists, as it seeks to pressure Taipei into accepting the one-China principle, which President Tsai Ing-wen has refused to do during her two terms in power.
Observers also called the adjustment yet another punitive measure by Beijing following Lai’s victory in the January 13 election.
“Obviously, it is China’s response to the outcome of Taiwan’s presidential election,” Shen said, adding that he expected more similar actions from Beijing.
The election of independence-leaning Lai, who will succeed Tsai in May, has riled Beijing. It responded by wooing Nauru, one of Taiwan’s few remaining allies, to switch ties two days after the vote.
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Vice-President William Lai wins Taiwan presidential election as his party loses legislature majority
Vice-President William Lai wins Taiwan presidential election as his party loses legislature majority
Slamming the flight path change on Wednesday, Taiwan’s defence ministry said the unilateral adjustment would stoke tensions in the Taiwan Strait. The foreign ministry called it an irresponsible act that would undermine flight safety, demanding that Beijing stop the operations immediately and engage in talks with Taipei.
The Mainland Affairs Council, which plans Taiwan’s cross-strait policy, said Beijing’s claims that the changes aimed to ease the pressure of increased flights were politically motivated.
“Everybody knows that the mainland side has yet to fully resume its international flight operations after the Covid-19 pandemic,” it said. “[Beijing is] deliberately using civil aviation to package its improper political and military attempts to potentially change the status quo in the Taiwan Strait”.
“The mainland side is to bear any serious consequences affecting cross-strait ties if it obstinately insists on its move,” it said.
Taiwan is an inseparable part of China, Beijing’s TAO responded, saying there was “no existence of the so-called median line”.
Direct flights across the strait had resumed since last year to 500 flights each week operated by 14 mainland cities, it said.
The TAO also called on Tsai’s ruling DPP to swiftly lift its “unreasonable restrictions” on full direct cross-strait flights.
