The RTOM/RTOW tables are produced using a performance optimisation procedure to give the best possible take-off mass. This procedure uses improved climb performance and its associated increase in speeds to increase take-off mass.
High Speeds - To increase maximum takeoff mass or flexible temperature, when climb, or medium to distant obstacle limited.
Low Speeds – To increase maximum take-off mass when field length limited, or close in obstacle limited. Or, when at maximum flexible temperature (TMAX FLEX), and increased speed does not give any benefit.