03/18/2010 05:12 am ET Updated May 25, 2011

It's a Bird! It's A Plane! No, actually, it's Tons of Carbon?!

So I was wondering, why is it that commercial air travel is considered so non-green? It seems unjust that my efforts to live green all year are negated by a few flights to Sierra Club headquarters and a trip or two to visit my parents.

Most carbon calculators - but notably not ours at Sierra Club Green Home ( - penalize even the dark green citizen who is required to fly commercial for work. Let's say you're a sales manager, you diligently recycle, you watch the thermostats, you have low-water landscaping, you eat organic vegetables, you're doing everything right except your job requires you to fly from Denver to Cincinnati twice a month. According to most evaluations, you are a serious carbon emitter. I don't think this is right, it's not fair to call this person a polluter. His or her lifestyle and home are green, and should be respected as such.

Although a pitch to the boss for teleconferencing in lieu of so many business trips is the best antidote, the real modern day quest is to achieve eco-friendly air travel. And what about the concept of full vs. empty flights? Nobody will dispute that the least green way to travel (sorry celebrities, CEOs and pro athletes) is by private jet. The amount of carbon produced vs. the number of people moved is not a favorable equation. Consider a 727 stretch packed with 300 people. It would seem that this calculation would be a lot more efficient in terms of carbon produced vs. passenger miles traveled. Kind of like watching a mom drive thru a Starbucks with her 25 pound kid in the passenger seat of a giant SUV - can it get more non-green? Whereas, you can justify driving a stretch Chevy Suburban if it is packed with six or seven passengers and their baggage, this is highly efficient per passenger mile, even at 15 mpg. A better way to quantify your transport emissions would be number of people miles moved per gallon.

Speaking of automobiles, the gains made in emissions control over the past 40 years are mind-blowing. As in, it would take about 50 2009 Corvettes to match the bad exhaust gases produced by one 1969 Corvette big block in an hour of driving. The introduction of computer-controlled engine management and high tech catalytic converters makes this possible. This also explains why the cloud of smog that used to hang over Los Angeles has dissipated significantly over the past few decades. You now can actually see the skyline!

So why, then, haven't airplanes matched this remarkable improvement demonstrated by the car industry? Or have they? To find out, we called Boeing, the world's largest maker of commercial aircraft. We spoke with Billy Glover, Managing Director of Environmental Strategy for Boeing's Commercial Airplane division. In this role, Mr. Glover is primarily responsible for all environmental aspects of the next generation of commercial jets that Boeing will build.

"Fuel efficiency of commercial jets has improved since the 60s by 70 percent," Glover declared. "This must be balanced with the economic consideration that our customers face: their number one cash expense is fuel. They demand improvements each time they order new aircraft."

The efficient marketplace has greatly improved fuel efficiency and reduced emissions accordingly. Not to mention, the noise, unburned hydrocarbons, carbon monoxide and other yucky stuff produced by commercial jets has been significantly reduced since the 90s. Indeed, take a look at the sky next time a big commercial flight passes overhead. Remember the deafening sound if the plane was below 5,000 feet? And how much visible smoke used to trail behind? That deafening noise has been replaced by near-silence, and those jet streams are for the most part no longer visible. What we are no longer seeing or hearing is technological improvement and reduced emissions. "This has been accomplished by a fundamental change in the architecture of the engine design. The high bypass engine moves higher volumes of air at lower speeds, thus noise is reduced and fuel is saved," explains Glover.

This is all great, but what's next for the sustainable airplane? Boeing and others, most notably Richard Branson's Virgin Air are working on commercial jets that will fly on sustainable biofuels. An industry trade group, Sustainable Aviation Fuels Users Group, is working to establish a sustainable biofuel supply that all aircraft can run on without costly conversions of existing jet engines. One example of biofuel in action was a test in January 2009 -- Continental took a Boeing 737 up for a test flight burning a 50/50 mixture of conventional jet fuel and biofuels. In this particular scenario the biofuel came from algae. The results indicated that this mix could work and it would save the airlines a lot of fuel expense dollars.

Hopefully, advances in jet engine efficiency and emissions control will accelerate, so that at some point our poor sales manager from Denver won't be penalized by the green world for having customers in Cincinnati. A lofty (I can't resist an occasional bad pun) but seemingly achievable goal.

Let's hear from you, as always we encourage and appreciate your comments. Is our sales manager green, or is he/she a carbon villain for flying? You decide. Thanks for reading!