At an airbase outside Tokyo, engineers inspect the ageing F-2 fighters that have patrolled the Japanese skies for decades.But with China’s newest stealth jets roaming ever closer, and the promised future of air defence still years away, Japan is growing restless.Its partnership with Britain and Italy to build a next-generation fighter has hit turbulence – and Tokyo may no longer be willing to wait.The sixth-generation fighter, part of the Global Combat Air Programme (GCAP), is slated to enter...