Instrument Meteorological Conditions

Instrument Meteorological Conditions (IMC) are weather conditions below the minimum visibility and cloud clearance requirements for Visual Flight Rules (VFR). In IMC, pilots must navigate by reference to cockpit instruments and follow IFR procedures.

• Generally defined as visibility below 3 statute miles or ceiling below 1,000 ft AGL
• Specific criteria vary by airspace class and country
• Flight in IMC requires an instrument rating and an IFR-equipped aircraft
• ATC separation and instrument approach procedures are used for safe operations
• IMC can be caused by clouds, fog, rain, snow, haze, or smoke
• Transition from VMC to IMC is a leading cause of VFR-into-IMC accidents (general aviation)