Aircraft are classified into approach categories (A through E) based on their Vref (reference landing speed) or 1.3 × stall speed in landing configuration (Vso) at maximum certificated landing weight. These categories determine the minimums (MDA/DA, visibility, circling radius) to be used on instrument approach charts. The system ensures that approach procedures are tailored to an aircraft's maneuvering capability and required obstacle clearance.
Example: If a Cessna Citation Mustang flies final at 125 kt, it must use Category C minima—even if certified as Category B.
Approach charts will include these lines under the Landing Minima or Circling Minima section.