To assist in the comparison of different countries' air force officer rank insignia, NATO rank codes have been used. These are established codes for determining the seniority of officer and other ranks in NATO countries for a particular joint task group or command structure, although specific appointments designate a higher level of seniority over other equivalent rank codes in a given situation. Officer ranks go from OF-1 up to OF-10; OF(D) being a special category for trainee officers awaiting a commission. The system should not be confused with the pay grades used in the US military. While countries outside the NATO command structure (including some NATO member countries such as France) do not strictly fall into this classification structure and there may be incidences of overlap the co