Rather than an F-35 or a Typhoon with new trim and chrome hubcaps, these emerging combat aircraft are set to represent a real sea change in tactics and, perhaps, strategy in the middle of the 21st century. But what exactly is the sixth gen? Let's take a look.

The year is 2044 and the place is the frontier between the Blue and the Green nations. The armed forces of the Greens is a little bit behind the times but, though they rely on a mix of fourth- and fifth-generation fighters, they have recently purchased a state-of-the-art surface-to-air anti-aircraft missile (SAM) system backed up by the latest in radar installations.

So far, the war that had been declared between the two countries had been a month-long standoff, but one day at about dawn an airborne early warning radar aircraft detected what it first thought was a small bird, except this was a bird that was flying at twice the speed of sound.

Initially thought to be a cruise missile, the Green defense forces quickly determined that it was a single stealth fighter plane of the Blue Air Force on a course that would soon put it in Green airspace. The alarm was sounded, the missile batteries put online, and a squadron of interceptors scrambled to engage the intruder.