I talked to a pilot for the RAF, and he was talking about how in practice, he would train in a Tornado, or something like it, and would hone his pseudo missile towards the helicopters he was training with. He'd mention how the alarm does go off both for choppers and aircraft. The reason being is that missiles do either a radar lock, or a heat sensing lock. IN turn, the sensors on aircraft can pick up these locks and senses, and it used to be the pilot had to pop flares, but most modern aircraft pop flares automatically.