Revenue passenger kilometres (RPK) is a measure of the volume of passengers carried by an airline
A revenue passenger-kilometre is flown when a revenue passenger is carried one kilometre.
A passenger for whose transportation an air carrier receives commercial remuneration is called a revenue passenger. This excludes passengers travelling under fares available only to airline employees and babies and children who do not have a seat of their own.
The RPK of an airline is the the sum of the products obtained by multiplying the number of revenue passengers carried on each flight stage by the stage distance - it is the total number of kilometres travelled by all passengers.
RPK is a measure of sales volume of passenger traffic.