Abbreviation for "revenue passenger kilometer," it is one of the benchmarks for measuring the size of airlines. If an airline flies a plane carrying 100 paying passengers 1,000 kilometers, that flight would count for 100,000 RPK's toward the airline's total. Deadheading crewmembers, standby passengers, and the like do not count toward the total. Empty seats also do not count toward the total.

The RPK is the preferred way of measuring an airline's size over simple passenger carriage or fleet size figures, because:

  1. It distinguishes between airlines with large and small route networks. British Airways, for instance, doesn't carry as many passengers as US Airways or All Nippon Airways, but is clearly a larger airline in scope and would turn over more RPK's in a year.
  2. As a corollary to the above, it better approximates how much money an airline makes and spends in its operations, because larger aircraft on longer routes make, and cost, more money.
In terms of RPK's, the top 10 airlines in the world are:

  1. United Airlines
  2. American Airlines
  3. Delta Airlines
  4. Northwest Airlines
  5. British Airways
  6. Continental Airlines
  7. Air France
  8. Lufthansa
  9. Japan Airlines
  10. US Airways
The ASK is sometimes used for the same purpose, but is considered a less reliable statistic. The FTK is used to rank cargo carriers.