Air travel has been the focus of much scrutiny lately due to its devastating effects on the environment. How will the aircraft of the future address this problem?

What sounds like a distant vision of the future is already possible today – at least when it comes to technology. Will quadcopters and "soulless" unmanned aircraft soon be transporting hundreds of passengers over long distances?

Freaked out by the idea of a pilotless plane? How about one without any moving parts at all – no turbines, no propellers? The next generation of aircraft could involve ion propulsion, which allows planes to take off and land anywhere – all without making a sound.