An aircraft landing weight determination system that is configured to determine an accurate gross weight of an aircraft, the aircraft landing weight determination system comprising: a gross weight determination control unit that is configured to determine an accurate gross weight of an aircraft at a point (106, 110) during a flight between a departure gate at a departure location and an arrival gate at the arrival location based on a first source of gross weight data of the aircraft, and a second source of gross weight data of the aircraft determined from measurements in the flight, including measurement from one or more onboard fuel sensors; characterized in that the first source of gross weight data is a first gross weight based on pilot input of the departure gate gross weight when the aircraft is at the departure gate minus fuel weight determined based on a calculated fuel burn between the departure gate and the point assuming a constant decrease in weight during flight, wherein the gross weight determination control unit is configured to: compare the first gross weight to a maximum weight threshold in response to determining that the first gross weight is not constant during at least a portion of the flight to determine if the aircraft is in an overweight condition; wherein determining that the first gross weight is not constant comprises determining a decreasing slope of the first gross weight as fuel is burned is not constant; and compare the second gross weight to the maximum weight threshold in response to determining that the first gross weight is constant and the second gross weight is not constant during at least a portion of the flight to determine if the aircraft is in an overweight condition; and determine that the aircraft is in an overweight condition when the first gross weight or the second gross weight exceed the maximum weight threshold. a gross weight determination control unit that is configured to determine an accurate gross weight of an aircraft at a point (106, 110) during a flight between a departure gate at a departure location and an arrival gate at the arrival location based on a first source of gross weight data of the aircraft, and a second source of gross weight data of the aircraft determined from measurements in the flight, including measurement from one or more onboard fuel sensors; characterized in that the first source of gross weight data is a first gross weight based on pilot input of the departure gate gross weight when the aircraft is at the departure gate minus fuel weight determined based on a calculated fuel burn between the departure gate and the point assuming a constant decrease in weight during flight, wherein the gross weight determination control unit is configured to: compare the first gross weight to a maximum weight threshold in response to determining that the first gross weight is not constant during at least a portion of the flight to determine if the aircraft is in an overweight condition; wherein determining that the first gross weight is not constant comprises determining a decreasing slope of the first gross weight as fuel is burned is not constant; and compare the second gross weight to the maximum weight threshold in response to determining that the first gross weight is constant and the second gross weight is not constant during at least a portion of the flight to determine if the aircraft is in an overweight condition; and determine that the aircraft is in an overweight condition when the first gross weight or the second gross weight exceed the maximum weight threshold. compare the first gross weight to a maximum weight threshold in response to determining that the first gross weight is not constant during at least a portion of the flight to determine if the aircraft is in an overweight condition; wherein determining that the first gross weight is not constant comprises determining a decreasing slope of the first gross weight as fuel is burned is not constant; and compare the second gross weight to the maximum weight threshold in response to determining that the first gross weight is constant and the second gross weight is not constant during at least a portion of the flight to determine if the aircraft is in an overweight condition; and determine that the aircraft is in an overweight condition when the first gross weight or the second gross weight exceed the maximum weight threshold.