How common is it for military helicopter pilots to fly with night-vision goggles? For military pilots, night-vision goggles are used just as commonly as they are by troops on the ground.

The crash of a Marine helicopter, like the one shown, that killed five Marines was ultimately caused by pilot error, but night vision goggles and unsafe flying conditions also likely were factors ...

The night-vision goggles, supplied by Washington-based Rigel Optics, are usually the stuff of stealth military missions and stakeouts.

DARPA, the Pentagon research arm, wants troops to have night vision that is as lightweight and compact as a pair of regular sunglasses.