One paying passenger flown one mile. It is the principal measure of airline passenger traffic.

A measure of airline traffic, a revenue passenger mile represents one paying passenger flown one mile.

RPM - One paying passenger carried one mile; a unit of measurement in the airline industry.

One revenue passenger transported one mile in revenue service. Revenue passenger miles are computed by summation of the products of the revenue aircraft miles on each interairport segment multiplied by the number of revenue passengers carried on that segment. ( Small Air Carrier Statistics )

Revenue passenger miles (RPMs) is a measure of a passenger traffic for an airline flight, bus, or train calculated by multiplying the total number of revenue-paying passengers aboard the vehicle by the distance traveled measured in miles. The calculation can be more complex for long-distance buses and trains (and some planes) where passengers may board and disembark at intermediate stops. Non-revenue-paying passengers (e.g., airline employees flying on free or nearly-free passes, passengers using complementary tickets, etc.) are excluded when measuring RPMs.