The way Heat Seeking missiles are portrayed in this game is extremely unlike the way such missiles behave in real life.
In ArmA, heat seekers have always been locking weapons, utilized by pressing the 'target' key to lock on to the target. The player waits until a lock tone is achieved, then fires the missile.

In real life, the pilot can only point the plane in the direction of the target. Seeking the target is entirely in the control of the missile. The pilot places the target aircraft within the HUD area that designates the boresighted missile's seeker cone. As the missile tracks the target, the buzzing tone in the cockpit increased in pitch. Once the tone indicates a clean lock, the pilot may release the missile.

Ingame, this could be simulated with a circular sight on the HUD (similar to the Bomb sight). When the target is inside the circle, the missile will begin to lock in the same manner as the Arma 2 Stinger missiles did. The square/diamond lock indicator could either be visible or invisible.

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