Taiwan has protested against China's "unilateral" adjustment of civil aviation flight routes that could result in civilian aircraft flying closer to the sensitive Taiwan Strait median line, adding pressure on Taipei in its aviation safety and aerial defense. China's Civil Aviation Administration said it in a statement Tuesday it will cancel a "veer-off measure" for all southbound flights operating on the M503 flight route, which lies just west of the median line — an informal demarcation point that Beijing does not recognize but until recently largely respected — and within the Shanghai Flight Information Region. This means all southbound flights will no longer need to veer off six nautical miles to the west from the designated route — as agreed by Beijing and Taipei in 2015 — and can now fly on the original path, bringing the aircraft closer to the median line and the Taipei Flight Information Region. The statement also said China will start operating on two ancillary routes connecting M503 with the cities of Fuzhou and Xiamen in Fujian province, which Taipei says could impact safety for its civilian aircraft flying in and out of Matsu and Kinmen, two outlying Taipei-controlled islands close to the shores of China. In response, Taiwan's Civil Aviation Administration says it "deeply regrets and firmly protests" China's decision, while the Mainland Affairs Council (MAC), Taiwan's China policymaking agency, calls the attempt "a blatant neglect of aviation safety and a show of disrespect for Taiwan." China's move "deliberately masks its ill political and possibly military motive against Taiwan in the name of civil aviation that could alter the status quo across the Taiwan Strait," the MAC said. China's ruling Communist Party claims the self-governing democracy as its territory despite never having controlled it, and has spent decades trying to isolate it diplomatically. In 2015, China unilaterally declared the operation of M503 route, prompting protests from Taipei. After negotiations with Taipei, Beijing agreed at the time to move the route six nautical miles to the west of its original path. The median line dividing China and Taiwan has been a tacit understanding between both sides not bound by any legal pact. Beijing has never formally recognized the existence of such a line, and in recent years has sent military jets across the line on a near daily basis, as it ramps up military pressure on the self-ruled island. — CNN