What is the Ratings API?

The Ratings API provides on-time and delay-based ratings. Two query types are available:

- by Flight, defined by a carrier code and flight number (e.g., HA 25)
- by Route, defined by departure airport and arrival airport (e.g., PDX to HNL)

The Ratings response includes percentage and “stars” ratings. The Stars number represents a rating on a scale of 1 to 5. See the Ratings Response for details.

Please see:
https://developer.cirium.com/apis/flightstats-apis/ratings#section/Introduction

Please note: 
Ratings API data may not available for a given schedule if the sample size is not large enough. This may happen if there is not enough available data, if the flight is new, or if the airline recently changed the flight number. Ratings API data is computed twice a month for the previous two calendar month window.