Space-age helmet for fighter jet pilots costs US$400,000 and links visor to cameras embedded in plane's skin

The F-35 Lightning II is one of the most complicated weapons systems ever developed, a sleek and stealthy US fighter jet years in the making that is often called a flying computer because of its more than 8 million lines of code.

The Joint Strike Fighter comes in three versions, including one that is designed to take off and land on an aircraft carrier and another that lands vertically, as if it were a helicopter.

But to truly understand the most expensive weapons programme in the history of the Pentagon, forget the plane for a minute. Consider the pilot's helmet, which costs US$400,000 apiece.

It's designed to protect the pilot's head, of course. But compared to everything the helmet does, protection becomes something of an afterthought.

The helmet sees through the plane. Or rather it helps the pilot see through the plane. When the pilots look down, they don't see the floor of the plane; they see the world below them. If the pilots look back, they see the sky behind them.

Embedded in the skin of the aircraft are six cameras, and when the pilots move their heads to look in a particular direction, they are actually seeing through the corresponding camera, which sends an image to projectors inside the helmet that beam an image of the outside world on the helmet's visor.