Which of the following is NOT a conventional threat to US Army aviators?

Helicopter mines are not considered a conventional threat to US Army aviators. Typically, conventional threats encompass direct threats to aviation that are usually well-understood and established within traditional military engagements. These threats primarily include anti-aircraft artillery, guided missiles, and fighter jets, which are designed specifically to target and engage aircraft.

In contrast, helicopter mines are not a common method of targeting traditional aviation. Mines are generally fixed explosives designed to be triggered by the movement of vehicles or personnel, and their role in air warfare is quite limited. The primary threats to aerial assets are typically focused on direct engagement methods such as anti-aircraft artillery and guided missiles that actively seek to intercept and destroy aircraft. This context helps clarify why helicopter mines would not fall under the category of conventional threats aimed at US Army aviation.