If your company is committed to reducing its airline-related carbon emissions, you need to start by re-thinking your cabin policy. This is the single-most important factor in a travel program’s impact on travel-related emissions.
It turns out that flying business class is better for the climate than flying economy class. Hard to believe, right? I was guilty of promoting the business-class is-bad belief back in 2007 when I led the development of TRX’s groundbreaking airline carbon emissions model. Chalk it up to some lazy thinking on my part, and please accept my apologies.
I make the new case why we need to fly business class in this Op-Ed at Business Travel News: https://www.businesstravelnews.com/Management/Why-We-Need-to-Fly-Business-Class
Yes, the optics of adopting a business class cabin policy will be tough to overcome, but if your company is serious about reducing its airline-related emissions, it is the right way to go. Comments welcome here and on LinkedIn at https://www.linkedin.com/feed/update/urn:li:activity:6830486638385233920/
Gillespie's Guide to Travel Innovation 
Interesting idea that I’d like to see validated by an airline. Comes down to whether weight is really the key driver for airline emissions. If true, an airline would need to have more business class seats than coach and charge a fortune for each. Not really practical on many levels. In addition, cargo flights would need to be compared to cargo ships potentially making them much more expensive and impractical. In the end thou, nothing worse than nearby traveler emissions on a flight ;-).
Thanks for (ahem) weighing in, Steve. Weight is absolutely the key factor, everything else being equal (engines, altitude, weather, distance, etc.). The airline would need fewer business class seats than economy so long as the business class fares are at least 3 times the economy fares; pretty much a given.