All of a sudden, the US Air Force is considering cancelling a multibillion-dollar effort to develop a new stealth fighter. Citing the high cost of the so-called “Next-Generation Air Dominance” programme and the competing demands of other projects, USAF leaders have warned they may have no choice but to cancel NGAD – and find other ways of winning control of the air in future wars. It’s a startling development for advocates of American air power. For generations, the whole US military – not to mention the militaries of America’s closest allies – have depended on the US Air Force to...