There is a demand from the public that the airline industry should show good will to fly more environmentaly.
See, that's where your problem is: there is decidedly NOT any demand from the PUBLIC that airlines will fly more environmentally friendly. Frankly, you don't have to be a rocket scientiest to figure out that flying is inherently un-friendly to the environment; but people still fly.
There's the politicians, the environmentalish and the fashion-conscious marketers who drive the hype. The rest of us know that taking that holiday in Spain may not be as environmentally friendly as staying at home and growing our own vegetables and singing kumba-ya, we just don't give a rat's ass. The neighbour is going so why shouldn't I? And when the flight cost's less that the parking fee at the airport...
To answer your question, it's easy as pie: use newer aircraft and fill up the seats for the lowest emission
pr person
pr mile. "Green approaches" have f all to do with emissions, it has to do with economics, and the free sensationalist publicity.