For a simple one way search, our partners can provide hundreds of options for a traveler. Providing a very large list of itineraries for a given search can be daunting for the traveler; thus we have created the Flight Quality Score (FQS) which helps us predict the relevance of itineraries as inferred by historic traveler search behavior.
The FQS is an itinerary ranking based on the objective best trade-off of price, duration and other attributes of the itinerary.
It mainly impacts the order in which itineraries are displayed - for example, it determines what travelers get shown first as the "best" flights, as seen here:
The "Best" sort order is now the default display to our users when they first perform a search. This sort order is based on the FQS and not on certain airline or OTA partners.
In addition, the FQS also plays a role in helping us decide which self transfer itineraries to prioritize and show our users (for more information about self-transfer itineraries please see our documentation):
At the moment, the FQS is configured uniformly for every search/partner/market so we would not be able to influence it for a specific partner, route, or market.