Commentary Last month, the United States and Europe approved a halt in their 17-year trade dispute over subsidies to Boeing and Airbus. Furthermore, both sides agreed to “collaborate on addressing non-market practices of third parties that may harm their respective large civil aircraft industries.” This means China. China is trying hard to break into the commercial airliner business, a lucrative sector dominated by the Boeing-Airbus duopoly. One might think that such a business would be ripe for more competition, and yet no other segment has been so hard to break into. The global civilian aircraft sector is an elephants’ graveyard of ambitious programs—the Mitsubishi SpaceJet, Sukhoi’s Superjet 100, Turkey’s TRJet—that have all failed miserably. Only Embraer of Brazil has succeeded in offering Boeing and Airbus any meaningful competition, and only by carving out a niche building small regional jets. So why does China believe that it can join the “big …