Quality of service index (QSI)

Quality of Service Index (QSI) is a metric used in the airline industry to evaluate how attractive a specific flight or route is to passengers. It was developed by the US Civil Aeronautics Board (CAB) in the 1970s.

The index considers several factors, including total travel time, number of stops, type of air carrier, and minimum connection time. A higher QSI indicates better service quality and greater passenger appeal.

Airlines use QSI data to compare route performance and identify market opportunities. For example, a direct flight operated by a full-service carrier (FSC) from a major hub airport will likely have a higher QSI than a longer itinerary with stopovers. This makes the index a helpful tool for route planning and competitive positioning.