The take-off and landing weight will be constrained by either a structural limit or a performance limit, influenced by environmental conditions on the given day.

Regulated Landing Mass 
The regulated landing mass (RLM) is the lowest of the performance limited landing mass and maximum structural limited landing mass. The actual landing mass must not exceed this limit.

Performance Limited Landing Mass 
The performance limited landing mass (PLLM) is the maximum permissible total aircraft mass subject to the landing aerodrome or site limitations also taking the current metereological conditions into account. This limit is not a set figure and needs to be calculated for each sector. If the PLLM is exceeded the aircraft may overrun the landing distance available and a go-around might not be achievable.