…when airlines talk about how they’re going green. A few airlines sent out press releases for Earth Day yesterday, and I noticed that Delta announced that the airline had achieved an “improvement of fuel efficiency by 35 percent since 2000.”
Now, I’m not exactly what Delta is using to calculate “fuel efficiency,” but I have seen airlines talk about how they’ve decreased their fuel consumption. The airlines have made good progess in this area whether it be switching to newer aircraft, installing winglets, cruising more efficiently, etc., and these do indeed help iwth fuel usage. But cutting ASMs by a decent margin also reduces fuel burn. 
I wonder how high that number would have been had they not taken on a bunch of Northwest DC-9s?