The Median Line in the Taiwan Strait: A Dangerous Loophole

Taiwan’s options are limited, but the Tsai administration must pursue a course of action that shows firm decisiveness and yet does not fall into Beijing’s trap. 

On March 31, People’s Liberation Army Air Force (PLAAF) warplanes flew across the “median line” in the Taiwan Strait that has long served as an unofficial airspace boundary between Taiwan and China. This behavior was unusual and provocative move on China’s part — the first time in 20 years that such a deliberate incursion took place. 

The incursion was brief and ended with the J-11 fighters being escorted and turned back by Republic of China Air Force (ROCAF) interceptors. But Taiwan’s subsequent response was firm: President Tsai Ing-wen declared that Taiwan would “forcibly expel” Chinese warplanes from the Taiwanese half of the Strait the next time such an intrusion occurred.

While Tsai’s resolve is commendable, such a stance could prove more problematic than anticipated. The issue is not simple; the airspace over the Taiwan Strait is delineated in a way that plays to Beijing’s advantage and Taiwan’s disadvantage. If played the wrong way, this could backfire on Taiwan and give China a public relations benefit.

The United Nations Convention on Laws of the Sea (UNCLOS) grants nations jurisdiction over their territorial airspace. This consists of the airspace over one’s land territory as well as the airspace above one’s territorial waters (all waters within 12 miles of one’s coastline, with some exceptions.) It has long been common practice for nations to fly warplanes near an adversary’s territorial waters without actually transgressing the official airspace in question, such as Russia’s periodic bomber flights near U.S. coasts.

But such jurisdiction does not apply to the airspace in the March 31 incident. The median line in the Taiwan Strait is not recognized by international law and neither side is technically violating the other’s airspace by crossing it (China does not officially recognize it). Most of the airspace over the Taiwan Strait, including the “median line” in question, is open-water airspace, free for international transit by all. The exception would be Penghu and its associated Taiwanese airspace and territorial water, but that region is easily avoided by Chinese warplanes. The convention that neither side’s warplanes shall cross the line is nothing more than an informal agreement. In other words, if Taiwan were to shoot down a Chinese warplane that crossed the median line, international law would hold China to be in the right and Taiwan to be in the wrong.

If Taiwan were to shoot down a Chinese warplane that crossed the median line, international law would hold China to be in the right and Taiwan to be in the wrong.

This creates a “bait” loophole that is ripe for exploitation by China. Beijing could fly PLAAF warplanes across the median line with impunity while claiming that any Taiwanese shoot-down of such warplanes amounts to a violation of international law and an act of aggression (provided that the shoot-down takes place beyond Taiwan’s “official” airspace: 12 miles past the Taiwanese coast). In essence this means that China gets to have its cake and eat it too; it can fly warplanes across the median line and achieve much the same psychological effect as violating Taiwan’s airspace while not having actually legally violated Taiwan’s airspace.

Additionally, China regards Taiwan to be its own territory in any case and would not consider international law to apply. From Beijing’s perspective, sending Chinese warplanes into Taiwanese territory is more akin to flying warplanes over Hainan Island than over a “truly” foreign country such as Russia or South Korea. Chinese warplanes could take matters further yet and fly within 12 miles of the Taiwanese coast outright or even over Taiwanese land itself — and claim that any Taiwanese shoot-down is an unwarranted “act of aggression” since China was simply “flying over Chinese territory.” China holds most if not all of the cards on this issue. Indeed, China appears to be possibly heading down that very course of action. 

Contemporary history is not encouraging in this regard. The EP-3E Aries II spy plane Hainan Island incident in April 2001 illustrates China’s willingness to contest airspace far beyond its own territorial borders, and the recent M503 air-route activation by Chinese authorities in January 2018 illustrate Beijing’s propensity to act unilaterally on Taiwan Strait-airspace matters. Furthermore, the Xi Jinping administration is and has been aggressively pushing the envelope and changing the “status quo” across the Taiwan Strait.

President Tsai has promised to “forcibly eject” Chinese warplanes that cross into the Taiwanese half of the Strait, but this leads to the question of how. Taiwan technically has no legal right to shoot down such aircraft before or unless they have actually entered within 12 miles of the Taiwanese coast itself. Therein lies the trap: Shooting down Chinese warplanes before they have entered the jurisdiction of Taiwan’s “true” airspace could lead to conflict escalation as well as international censure, with Beijing portraying Taiwan as the “aggressor.” But by consistently crossing the median line and daring Taiwan to shoot down Chinese aircraft, Beijing could also call Taipei’s bluff and make the Tsai administration appear impotent. 

A less-than-lethal method of enforcement is desirable in such a situation. Traditionally, fighter escorts have fired tracer warning shots when a hostile aircraft is behaving uncooperatively during an intercept, but Chinese warplanes might deliberately disregard the warnings and persist so as to force Taiwan’s hand into a shoot-down. A potential recourse would be to employ the electronic capabilities of ROCAF warplanes. Active electronically-scanned array (AESA) radars, for instance, are speculated to possess a directed-energy function with which to inflict damage on hostile electronics. The ROCAF’s entire F-16A/B fleet is currently being upgraded to F-16V Viper standard, which entails being outfitted with the Northrop Grumman AN/APG-83 Scalable Agile Beam Radar (SABR), an AESA system — however, only a tiny number out of Taiwan’s F-16 fleet has been thusly modified as of time of writing. (Decay of radar energy with distance would not be an issue; the intercepting Taiwanese F-16Vs would presumably be within extremely close proximity of the Chinese warplanes being intercepted; possibly mere dozens or hundreds of meters.) Whether the SABR AESA is capable of such directed-energy function or not is likely something the general public would not be privy to, but if it is, it could be an ideal less-than-lethal force option in such intercept situations.

Additionally, if China begins crossing the median line on a regular basis, Taiwan should then consider “normalizing” it by having ROCAF fighters cross over the median line from time to time in like fashion. Taiwan would have a geographic advantage in already possessing and administering the land territories of Kinmen, Matsu and Penghu and the airspace immediately above and around them. The presence of Taiwanese antiaircraft batteries on offshore islands and at Makung Air Force Base in Penghu also further bolster Taiwan’s geographic advantage in the Strait. For the sake of precedence and establishing who the true “escalator” is, it would do Taiwan well not to shoot down any Chinese warplane that crosses the median line until or unless China has done the same to Taiwanese warplanes that cross the line into the Chinese half — otherwise Beijing could very well argue that Taiwan shot down Chinese jets in a way that China would not have done.

It should be noted that by reacting so strongly to a Chinese incursion into the Taiwanese half of the Strait, Taipei is playing into Beijing’s hand by giving China psychological power over Taiwanese perceptions. The appropriate approach should be for Taiwan to “normalize” such incursions by downplaying them in the media and also by sending ROCAF fighters across the line just as frequently — or by using less-than-lethal force on Chinese warplanes as an intermediary solution. Taiwan’s options are limited in this Strait situation, considerably more so than China’s. Nevertheless, the Tsai administration must pursue a course of action that shows firm decisiveness and yet does not fall into Beijing’s trap. 

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