The sum of the products obtained by multiplying the mass of freight, mail, passengers and that of their luggage, carried on each flight stage by the airport-to-airport distance.

To calculate the mass of passengers and their luggage, an air carrier has to convert the number of passengers into their mass using a conversion factor at the discretion of the air carrier and add the mass of their luggage, or assume that the mass of one passenger and their luggage equals to 100 kg.