Editing Instrument meteorological conditions (section)

===Visibility and separation from clouds===
With good visibility, pilots can determine the [[aircraft attitude]] by utilising visual cues from outside the aircraft, most significantly the [[horizon]]. Without such external visual cues, pilots may be subject to [[Sensory illusions in aviation|sensory illusions]] and must use an alternative reference for the attitude, which is usually provided by gyroscopically-driven instruments such as the [[attitude indicator]] ("artificial horizon"). The availability of a good horizon cue is controlled by meteorological visibility, hence minimum visibility limits feature in the VMC minima. 

Because the basic traffic avoidance principle of flying under [[visual flight rules]] (VFR) is to "see and avoid", it follows that distance from clouds is an important factor in the VMC minima: as aircraft flying in clouds cannot be seen, a buffer zone from clouds established by the minimum separation requirements provides for time to react to an unseen/unknown aircraft exiting the clouds, especially when air traffic control may not be enforcing aircraft separation (as in airspace classes C-G).