Military helicopters often fly tactically at night, which necessitates the use of Night Vision Goggles. NVGs decrease the pilot's field of vision to 40 degrees, and decrease visual acuity to 20/50 at best. Also, the darker the night, the poorer the performance of the goggles, because the goggles only amplify available natural light. On a bright, moonlit night they work fantastically well, but with no moon, or an obscured sky, they woork poorly. For example, Late February, 1991 in the Persian Gulf, there was almost no available natural light, due to obscuration of the sky by smoke from the oil well fires. In these conditions, the goggles are almost useless. Yet, combat dictates that operations continue despite the conditions. And even in the best of conditions, you can't see wires; you have to look for the poles in order to avoid wires.

Military helicopters almost always fly in sections of 2 or more aircraft, so there is always another aircraft to maneuver with and around. Of course helicopter operations take place in close proximity to the ground. Nap-of-the-earth flight requires extreme concentration. When you combine the workload of simply flying the helicopter, with maneuvering tactically, maintaining combat situational awareness, communicating with radios, leading flights of multiple aircraft, and delivering ordnance or landing troops, the potential for a mishap increases exponentially.

Throw in some bad weather on top of all that, as is commonly encountered with shipboard helicopter ops, and you've got the most difficult environment possible. If you consider all possible kinds and regimes of flight, tactical helicopter operations are the most difficult and hazardous.