Passenger-kilometres by air expressed as a percentage of available seat-kilometres.

The passenger-kilometres offered for the carriage of passengers by air transport is the sum, for all flights, of the products of available passenger seats in a given flight by the length of the route of that flight. In the case of multi-stage flights (flights with stops other than technical ones), the calculations should be made for all flight stages. The unit of measure for passenger-kilometres (performed, offered) is the passenger-kilometer.