Written by Michal Thim.

China officially launched the new M503 commercial flight route on March 29 — right in the centre of the Taiwan Strait. Initial reactions in Taipei were of surprise and rejection, which suggests that relevant government agencies in Taiwan were left in the dark before Beijing made the announcement.

Taiwan objected on the grounds that the new route endangers air safety because it comes very close to the median line and training areas used by the Taiwanese Air Force (ROCAF). To better understand those concerns, it is necessary to imagine an airspace as being divided into two kinds of skies, each with its own set of rules that need to coexist in an increasingly crowded environment. One is the strictly regulated sky for commercial transportation, while the other is the realm of air forces that are mostly free from international regulation, other than respect for other states’ territorial airspace and self-imposed codes of conduct. Although the rules for military and government aircraft on one side and commercial and private aircraft on the other are different, the sky remains a space that must be shared by everybody.

Beijing can claim that it is following regulations and contributing to air safety. Who would oppose that? However, Taiwan has a fairly legitimate reason to oppose M503 based on the right to use airspace for training and exercises. In theory, that should not be too complicated. Commercial planes follow a scheduled path and scheduled times and military planes need merely avoid them. However, the two are normally kept at a distance. The ROCAF’s designated areas have been in place for a long time on Taiwan’s side of median line, which Beijing has generally respected (and vice versa). Thus, to designate flight path just a few miles from those areas is irresponsible and potentially dangerous. Beijing’s decision is likely purely political.

To understand the particular conditions in Taiwan Strait, we need to understand what the median line is. Dividing the Taiwan Strait into two sectors, it was originally imposed by the U.S. in 1954 in order to keep the Chinese Nationalist Party (KMT) forces on Taiwan and the Communists in China from confronting each other. Gradually the line started to function as divide more or less respected by both sides. However, it is not a legally binding border. In theory, People’s Liberation Army Air Force (PLAAF) patrols and reconnaissance planes could fly as close as 12 nautical miles from Taiwan’s coast, and Taiwan’s could do the same. US reconnaissance planes actually do just that on regular basis.

The situation became more complicated with the introduction of direct cross-Strait flights in 2009. Flights from China had to avoid ROCAF training areas by approaching Taiwan from the north, south, or via a corridor over the Penghu Islands. Despite the more crowded airspace, the training areas for the ROCAF remained. That changed in November 2013 with the introduction of the controversial Chinese Air Defense Identification Zone (ADIZ) over the East China Sea, after which the ROCAF vacated the RCR8 training area. The introduction of the M503 route further constrains the ROCAF because an unintended crossing of the median line now means crossing the path of commercial flights. To concede and move the training areas closer to Taiwan is a non-option, as busier and long-established commercial routes already exist.

Regardless of all the implications for ROCAF training, the M503 is still not a threat to national security — at least, not yet. If and when Beijing decides to put pressure on the ROCAF, it will do so overtly. For example, an increased number of patrols close to the median line that might cross into the Taiwan side “by mistake” and regular incursions into Taiwan’s ADIZ, similar to the one in August last year, would become the norm. Each of these actions would prompt the ROCAF to scramble interceptors (which would in turn help Beijing learn new information about Taiwan’s air defense response time). If done consistently and on a long-term basis, like Beijing does with Japan and Russia with Europe and with Japan, Taiwan’s capabilities would soon begin to wear down. The effects of the M503-related limitations would then add to the general exhaustion.

In essence, there is little that Taiwan can do at the moment. China opened the route on its side of the median line, which in any case is international airspace, and succeeded in maintaining the impression that its intentions are not sinister. But that is exactly the part that should worry policy makers in Taipei (and Washington). The introduction of the M503 air route  is part of a “salami slicing” pattern where Beijing is slowly but surely trying to introduce fait accompli violations of accepted practices and international agreements along its maritime border and beyond. In all those cases, Beijing may claim (more or less successfully) some legal grounds or legitimate concerns behind its decisions. However, in all cases, strings with Chinese characteristics are attached.

When the Taiwanese side expressed surprise and opposition to the new route, Beijing retorted that Taiwan should not be too suspicious. Indeed, opening a new route at a time of warming ties between Taiwan and China should be greeted with enthusiasm, it said. China’s Defense Ministry spokesman even called the M503 an “air passage of peace.” The hard fact is that out of nowhere Beijing has presented a seemingly benign measure that nevertheless has an impact on Taiwan’s sovereignty, which Taiwan is hard pressed to respond to accordingly. This tactic will likely be seen again.

After Taiwanese officials initially protested on a security basis, National Security Bureau Director-General Lee Shying-jow (李翔宙) told legislators just before the route was launched that Taiwan’s security was not affected. What has Beijing done to deserve the change of mind? Not much. It merely retracted the plan for three east-west corridors that would join the M503 from the Chinese side and slightly moved the M503 route a few miles from the median line (10.2 nautical miles instead of the original 4.2). The current administration has invested so much political capital in presenting itself as the guardian of stable cross-Strait relations that strong resistance to M503 was virtually off the table as an option, especially because the KMT will once again play the “stability” card during the election campaign this fall. Beijing knows this very well. Thus, the government in Taipei formally agreed to the route. Not only did Taipei change its mind, but Washington also praised the agreement as a “positive sign” of cross-Strait cooperation. What if a different party — one that stuck to Taipei’s initial position and which Beijing was perhaps less willing to play nice(r) with — were in power in Taipei? Who would Washington then identify as the troublemaker?

The M503 route should not be seen in complete isolation from the changing dynamics in cross-Strait relations. Chinese President Xi Jinping (習近平) has said that China does not have endless patience regarding the unification of Taiwan. In September 2014, Xi insisted that “One Country, Two Systems” was still the right model for unification despite the failure of this model, as symbolized by last year’s Umbrella movement protests. The defeat of the KMT in Taiwan in the Nov. 29 local elections has prompted many to contemplate the likelihood of a KMT defeat in the general elections in January 2016, which would bring the opposition Democratic Progressive Party (DPP) to power, a less than desirable prospect for Beijing. The announcement of the M503 route took place against this background. Although Beijing would not openly admit that its motivations were political, the timing in this case is very peculiar.

In an ideal world, commercial airlines would refrain from using the route as it is their primary responsibility to protect their passengers from harm, intended or otherwise. Though a collision would have to be the result of an improbable chain of bad decisions and misfortune, no responsible air force commander wants to take such risks. Taiwan has the right to conduct exercises and train in well-established and designated areas without constraints other than standard safety precautions, yet it will be Taiwan’s air force that must compromise and limit itself to avoid putting civilian passengers at risk.

What this new route shows is that with Beijing exhibiting greater imagination and dexterity in manipulating the established rules, the Taiwanese government and its agencies had better prepare for more unpleasant surprises from Beijing in future.

Michal Thim is a Ph.D. candidate in the Taiwan Studies Program at the China Policy Institute (CPI), University of Nottingham.  Michal tweets @michalthim. Image Credit: CC Erik Törner/Flickr. A version of this post was originally published on Thinking Taiwan and is available here