https://www.heathrow.com/latest-news...ng-end-to-2019
"Our Fly Quiet and Green league tables revealed that more airlines are operating ultra-quiet and green 787s and A350s, partly in response to environmental pricing incentives."
Except that the tables don’t actually reflect that change at all -
airline fleet composition makes no difference at all to the average Fly Quiet score.
Because the Fly Quiet programme score per airline is based on relative, rather than absolute performance (i.e. Airline A is better/worse than Airline B), there is no appreciable difference in the average score per airline from one quarter’s results to the next.
In fact, the average Fly Quiet score awarded by Heathrow of 752 points per airline in the most recent table is LOWER than it was when the current scheme started in 2017 (762) !
See
https://www.heathrowflyquietandgreen.com/2019-qtr-3rd/