RPK, or Revenue Passenger Kilometers, is a key metric used in the airline industry to measure passenger traffic. It represents the number of kilometers flown by paying passengers. For example, if 100 passengers travel 1,000 kilometers, the RPK would be 100,000 kilometers. This metric helps airlines assess their performance and demand for flights. RPK is often compared to Available Seat Kilometers (ASK), which measures the total capacity available for passengers. By analyzing both RPK and ASK, airlines can determine their load factor, indicating how efficiently they are filling seats. This information is crucial for strategic planning and operational efficiency in the airline sector.