The Airline Industry Eyes Its Carbon Footprint

Regulators have begun scrutinizing airlines for their outsized carbon emissions. The industry looks for ways to lower emissions and maintain profits.

The airline industry accounts for two percent of global carbon emissions, and emissions are likely to increase as the popularity of air travel rises.  Policymakers are increasingly working with airlines to find ways to limit emissions growth.  But the diverse, global industry is difficult to regulate, and competitiveness issues abound. 

Megan Ryerson, professor of transportation at the University of Pennsylvania and an expert in environmental impacts of the air transportation system, provides insights into the airline industry’s environmental challenges and possible strategies to address its greenhouse emissions.

Andy Stone: Good day and welcome to the Energy Policy Now Podcast from the Kleinman Center for Energy Policy at the University of Pennsylvania. I’m your host Andy Stone. The airline industry is an enabler of our modern way of life, allowing us to travel far and wide to maintain relationships, explore and build businesses. Yet the industry is under rising scrutiny from policymakers for its more problematic contribution to global warming. Air travel accounts for a significant portion of worldwide carbon emissions and as travel continues to expand over coming decades, the industry will find itself increasingly at odds with efforts to fight global warming. Recently, the U.S. Environmental Protection Agency indicated that it would regulate airline carbon emissions, creating a challenge for American air carriers in an industry that is not only inherently global, but also bound to fossil fuels. Here today to talk about the issue as our guest, Megan Ryerson. Megan, welcome to the show.

Megan Ryerson: Thanks so much Andy.

Stone: Megan is Assistant Professor of Transportation Planning and Engineering at the University of Pennsylvania and a collaborator with the Kleinman Center on research into energy and emissions challenges that the airline industry faces. Megan, how has this focus on emissions come about and are emissions the next big challenge for the industry?

Ryerson: Andy, you are absolutely right. It has been a dramatic 15 years for the airline industry and I would say the aviation system as a whole. This question that you pose, where’s the focus of emissions from and are emissions the next big challenge is really central to my research program ever since I began in air transportation research. My first introduction to air transportation research was at a time when fuel prices were increasing dramatically around 2006, 2007. And the concern of aviation’s contributions to climate change and their GHG emissions was really growing.

And to me, the question that I was very interested in was a very practical one: at what price of fuel does sort of 300 mile air travel, you could think the California corridor or the Northeast corridor, at what price of fuel does it not become viable to have air travel in that corridor anymore? Or at what price of fuel do we switch to very fuel efficient but slower aircraft, maybe known as turboprops that were popular years ago. And being able to look at what I thought were practical solutions that can save fuel, can save emissions, and keep the aviation industry viable has really been a driving force for my research. And so now I maintain a research program that looks at planning processes, I design algorithms, and help to the industry forward in terms of reducing fuel consumption, being more adaptable to climate change, while continuing to thrive. Aviation is critical to our global, our national, and our local economies. And that’s really where my research is focused.

Airline emissions, aviation emissions, are a large and possibly growing portion of overall emissions. Globally, airline emissions are about 2%, 2 to 3% of global emissions. That’s about 8 to 11% of total transportation emissions. Just to put those percentages in context because they may seem a little bit small, you know, while aviation is only about 2 to 3% of global emissions, it is very hard to reduce aircraft emissions compared to reducing emissions from other modes. And basically there are two ways to reduce aviation emissions. There is technology, there’s advanced avionics, there’s new composite materials for aircraft. There are new air traffic management technologies that could allow aircraft to fly shorter routes. And then there’s demand management, which is, you could think of as policy ways to reduce flying or encourage people to take a more fuel efficient mode.

However, in many cases when we’re talking about air travel, there is no other fuel efficient mode. Aircrafts are actually relatively fuel efficient. If you’re looking at long haul travel, there’s some really great work coming out of up Mikhail Chester at ASU comparing the emissions of different modes and aircraft come out really well when you look at long haul travel and long haul travel is also not really viable in many cases unless you’re on an aircraft. So, we’re really looking at what technologies can we use to reduce emissions and in certain small cases, where could we possibly reduce some flying to save those emissions.

One of the other reasons why it can be so difficult to do, you know, demand management in air transportation is that air transportation, as I said and you said, is critical to our global national, local economies, right. And actually reducing flying is not a goal of any government. And it’s certainly not a goal of many of the travelers who are looking for more and more air travel. I want to give you some context as far as the scale of the emissions reduction challenge that we face in air transportation. In the case of Boston, their city estimated that their bike share program saved about 350 tons of greenhouse gas emissions over three years. That’s great. That’s a really successful program. When you compare that to a brand new international flight that Boston has that is nonstop to Beijing, the emissions for one year of that flight is 60,000 tons of CO2. So, you know, while I’m sure that flight is a boon to the economy and lots of people are taking it and being able to travel in a very efficient way, time efficient way to Beijing, the scale of the emissions for that flight completely swamps the savings that were made from a rather intense effort on the ground to save surface transportation.

Stone: So that flight out of Boston, every, that’s a daily flight. And are we talking about the one day’s emissions is more than the Boston bike share would save?

Ryerson: A year. A year of daily flights, yes.

Stone: Ok, I just wanted to clarify that. 

Ryerson: Yes, for one flight a day for a year.

Stone: Now you’ve mentioned that the airline industry is also particularly difficult to regulate. How so?

Ryerson: Aviation is difficult. It’s difficult to regulate on a number of different scales. Let’s start out with global. Aviation is a global industry and as a part of that, each nation feels that their competitiveness is tied to the competitiveness of their airlines and their aviation industry. There is a global sort of regulator of aviation. This is ICAO, the International Civil Aviation Organization, and you know, they set international standards and they also set international policy as far as, you know, how international flying will take place. If anything, ICAO and international aviation has become more and more liberalized throughout the years.

In the 1970s, international aviation was highly regulated. There were only a few international routes in the U.S. there were only a few airports that were allowed to handle international flights. Since the changes of the Open Skies Agreements, now, you know, airlines can fly or where they like. So global aviation can be very difficult to regulate because it’s a part of a nation’s competitiveness and because liberalization allows for more options. Similarly, in the U.S., regulating domestic aviation and limiting domestic aviation is pretty much the opposite of the goals of local governments and the federal aviation administration.

There was a long history, both in practice and in research, of understanding that local governments believe that airports and air service are the way to grow the economy. You often hear city managers call airports the growth engine of their city. In fact, the FAA about 10 years ago, the Federal Aviation Administration, allowed local governments to use money that they raise on airport from concessions from rental cars and things like that and use it to subsidize the airlines to open up new routes in the hopes of jump-starting the economy and building air service. So, you know, we do have sort of regulations there to support the growth of the aviation industry, nationally because local governments really want to grow their economy with growing air service.

Stone: So domestically and internationally, we have a situation over the last decade or so where regulation is actually liberalized markets, increased competition. How does that translate in potentially into more emissions, and a greater emissions challenge for the industry?

Ryerson: I’m going to give you a pretty detailed answer here because there are competing forces at play that are changing the way that we fly up both domestically and internationally. The short answer to your question is in the U.S. we’re seeing a slightly decreased domestic flying and internationally, we’re seeing big boons in international flying. You know, in the past 10 years, we briefly mentioned airline mergers. I mean, since 2007, major airlines have merged into three. And what did they do? They consolidated their networks. They cut unprofitable flying, which means that if you’re in a city like Atlanta or Dallas or, certainly New York or San Francisco, you’re probably seeing better air service. The airlines have strengthened their hubs in those cities. But if you’re in a small city like Chattanooga or Huntsville, Alabama, you are likely seeing decreased service because the airlines cut unprofitable routes.

And so we’re seeing a slight sort of downturn in domestic flying and short haul flying and that has environmental benefits. It has environmental benefits because in general, smaller aircrafts have higher emissions per mile. And so it’s more efficient to have a longer aircraft fly, a bigger aircraft fly a longer distance, rather than the smaller aircraft that admits basically the same amount per mile as a large aircraft but has fewer passengers. So that does have possible environmental benefits. I realized that it has disbenefits for the travelers, you know, less convenience and so on. On the other side, the liberalization of international aviation and the establishment of these sort of joint venture partners that allow the airlines to launch new service with lower risks, is leading to a dramatic growth in international aviation. Couple this with the Gulf carriers, Qatar and Emirates, as well as Turkish airlines that are really fighting for global domination, right? They have global airline networks and they’re all looking to sort of establish themselves as the international airline. We are seeing massive growth in international travel. Now as far as how that’s growing emissions. That is a very big question. Many of these airlines are adopting fuel efficient aircraft for their long haul trips. You know, the 787 is a great example. The Boeing 787, very fuel efficient international aircraft. So we’re seeing more international aviation, but we’re seeing it in general on more fuel efficient aircrafts. So it’s going up but it’s not going up as much as it could if we didn’t have these advances in avionics.

Stone: You’ve written about the fact domestically that as some of the short haul routes get diverted away from the regional airports, people might actually have to drive farther to get to the airport before they take their trip. And has there been much research on the balance of the emissions from that phenomenon?

Ryerson: Exactly. This concept that in the aviation industry we might call airport market leakage. The idea that people who live approximate to an airport that has low service might drive quite a distance, 2, 3, sometimes even 400 miles to a hub airport to get better service and to get lower cost service. It’s something that the airports have known for a very long time. It’s something that researchers are just picking up on now. There’s a much smaller body of research about airport market leakage. And I think one of the reasons that the body of literature on this phenomenon is because there used to be very high levels of air transportation service domestically. And since the airline mergers, we’re seeing a, a downturn in service and we’re seeing an increase in market leakage.

I’ll say just anecdotally, I had a discussion with the manager of a small airport about that’s located about 400 miles away from a very major hub airport. And this director told me that they see about 300,000 passengers a year drive that 400 miles to the distant hub. This is a real issue. And you know, when we’re talking about saving airline emissions, I think the bigger question is saving intercity transportation emissions because with this concept of market leakage, it’s not just the airline network, it’s an intercity transportation network of which air travel is a component. Right. And this is something that I’m working on currently and it’s a place that I’d like to take the conversation because I think that while we’re seeing some gaps in the airline network and we could hail that as savings, those people are still traveling. And how are they traveling? Are they traveling one by one in a car? Because we know, referencing back those comparative mode emissions research I mentioned, we know that if one person is in a single car, that’s nowhere near as good as having that one person on a full aircraft. Right? So that’s why I think we need to think of this as a network problem.

Stone: So it sounds like we have a situation where ridership is going up. You talked about globally more people are flying and the airlines are really competing hard to bring more people into the service. So in a sense it sounds like it may be a little bit out of step, the whole industry, with where we’re going in terms of our concerns for carbon and lowering emissions, et cetera. So what are the actual options to reduce emissions? What are the tools that are available?

Ryerson: So I think the tools that we have available to us fall in two general buckets. There’s technology and there’s demand management, right? And the technology bucket is very, very big. There is possible savings from air traffic management technology. So the Federal Aviation Administration is hard at work, developing next gen technologies or next generation air transportation system technologies and they’ve had some real success. Advanced avionics are allowing aircraft to execute more precise navigation, said more plainly, aircraft can approach the airport and land without taking sort of big swings around the airport. And in Seattle for example, the FAA found that they were saving six minutes per flight and that’s six minutes of a flight taken at low altitude, which is very fuel inefficient, much more fuel efficient to be at high altitude. And they found they were saving Alaska Airlines about 1% of their total flight fuel consumption per flight. That’s a really great gain.

So we have advanced avionics, excuse me, we have an advanced air traffic management, which is a way that we can get there. We also have technology actually on the aircraft. We have advanced engines. We have these advanced composites that make up the aircraft like the 787.  And in some cases, the 787 can be up to 20% more efficient than similar aircraft that don’t have those advanced composites and engines. So it’s really possible to get fuel efficiency gains, you know, from actually replacing aircraft with more advanced aircraft. So there’s those areas of technology.

Then there’s certainly biofuels. And every once in a while I hear a hydrogen mentioned, I think that’s much, much, further off. But we have in the aviation industry had a lot of successful tests with drop in biofuels. These are blends of traditional fuel and biofuel and their flights had been able to complete their mission as expected with these drop-in fuels. You know, a large scale rollout of biofuels would require very, very big changes in the industry. So I think we’re far away from that. But it certainly seems like a viable direction to reduce fuel consumption. And I should say the FAA is very hard at work on alternative fuels. They have a very active group within their environmental division researching biofuels. So that’s some of the sort of technology gains.

Then there’s this possibility to think about, you know, demand management. Again, you know there’s no one who wants to see a reduction in flying, you know from the sort of governments, perspective. And from the flying community perspective, there’s certainly environmental groups who have advocated for this. But when I think about demand management, I think of looking at routes where there might be another mode that could serve that route more efficiently. There’s been a lot of discussion of trains in the U.S. we have very limited train service, but you know, it could be possible, for example, when the California high speed rail is built that we’re able to, you know, reduce some flying and replace it with rail. It’s much more easy, it’s easier to electrify a car than electrify and aircraft. So, you know, maybe as we advance our surface transportation vehicles, it might make sense to get some really nice buses and replace some of these short haul routes to save fuel.

Stone: No electric planes?

Ryerson: No, no, no electric planes yet. And that’s what I’m talking about. Demand management. That is you know, that’s something that’s been studied. It’s less attractive because a bus doesn’t bring business development to a city the way a flight does. Right. So, you know that’s the sort of realistic spin on that. And you know, certainly the other way to save fuel is to stop flying or promote telecommunications in replacement for meetings. But you know, I think that what we found is that nothing beats a face to face. We as a people want to be connected and we want to be able to travel. So we may want to look at those other components.

Stone: Got it. Thanks. Yeah. Going back to the issue, very specifically of carbon emissions and global warming for a moment, these are going to become bigger issues over time. It’s pretty certain. What about the future impact on air travel as potentially carbon pricing comes into play? Can the airline industry escape? Will air travel simply become too expensive for the average person or for the airlines themselves to stay in business?

Ryerson: Right. I’ll answer this question in two parts and the first is that I think we’re pretty far away from carbon pricing in aviation. And the second will be the what if scenario in the future. Back in 2012, the European Union wanted to include aviation in their emissions trading system. The idea, very briefly, is that the EU hands out credits, carbon credits, to the polluters in the Union, based on the amount of CO2 they emitted in the past year. And then it’s on the industry to reduce their emissions and cover their emissions with the credits that they’re allocated, or to buy credits on the open market if they ended up polluting more than they did the past year. So the EU wanted to include all flights that touchdown at an EU airport in their emissions trading system.

The response from China and from the U.S. and from other countries was, you know, absolutely not. Developing countries whose aviation systems are growing incredibly rapidly, they didn’t want to be judged on last year’s performance because they’re growing their aviation system tremendously. And then countries like the U.S. with a very established aviation system, first of all, were concerned that such a move violated their international agreements that the member States had agreed to, you know, back in the forties about how they will, you know, interact and how they can regulate and charge one another. And also the U.S. was concerned about competitiveness and didn’t necessarily want to start paying and allocating credits for something that they view as a key to their national competitiveness. So the issue was dropped after a tremendous amount of pushback. And so when I think about carbon pricing for the airlines, I just think it’s something that we’re very far away from because it seems like all policymakers, regardless of party and ideology are out to protect their aviation industry.

That said, do I think that changes in policy could make air travel more expensive and too expensive? I think that it’s possible in certain markets, and I’ll give an example. There’s been a lot of press about airlines charging for luggage and that there’s been a lot of pushback from the air passenger groups, you know, saying that this is just adding to the ticket price and so on. And while there’s likely a true component to that, the airlines are actually doing very well on baggage fees and what these ancillary revenues. There’s a very physical relationship between the weight of an aircraft and the amount of fuel that aircraft burns. And so every additional pound of an item that you bring onto an aircraft, that aircraft is burning about a quarter pound of fuel. And this is actually, I published a paper on this topic looking at the relationship between weight and fuel consumption last year, actually supported by the Kleinman Center and some of my airline partners. And that physical relationship was behind some of the motivation to separate the cost of a ticket and the cost of bringing on additional baggage. And you could think of it if you’re a light traveler, you’re subsidizing people who are heavy travelers if you don’t have baggage fees, right?

 So it’s possible that we might see more of a relationship between how much fuel are you making us spend and how much you pay. That is absolutely possible. Another thing we might see with more policies or with something like prices is again more reductions in the short haul travel. Again, the idea that smaller aircraft have higher emissions per passenger mile. They have two engines. They burn basically the same amount of fuel as a larger aircraft, but they have fewer passengers on it. So if we really do have higher costs from fuel consumption, those higher costs are going to be felt more by small aircraft and flights on small aircraft than flights on large aircraft. And maybe it will just stop making sense to fly those routes.

And maybe we’ll see more of something I’m very interested in, which is this relationship between surface transportation, rail and auto, and bus, and air. And Continental, now United, but at the time Continental, actually had a partnership with Amtrak where they said, Newark is a very important hub to us, Newark, New York, but you know, it’s a capacity constrained airport, right? We don’t have, we can’t just have flights from everywhere and everywhere. We’re going to partner with Amtrak in the hopes that people in the Northeast corridor take Amtrak to Newark. And you could actually buy an Amtrak ticket through Continental’s booking service. And you could still do that on United, actually combine an Amtrak ticket to connect through Newark. And so maybe we’ll see more and more and more of that as the penalty for using aviation fuel gets bigger.

Stone: So it sounds like over time some of these shorter flights may go to trains, for example, to buses, people drive?

Ryerson: Right. We’ve seen that in a very big way abroad, right? In the U.S. we just have a limited rail system, but we’ve seen that in a very big way abroad. And as we possibly get some more train service, like I said in California, and you know, maybe again with buses or some sort of express surface transportation system, we might see that.

Stone: Now I’d like to just touch back on one issue we talked about just a few minutes ago just to kind of sum up here. And it’s the issue of competitiveness. Okay. And with this new agreement from the International Civil Aviation Organization, which per my understanding, will basically, the goal is to halt airlines emissions growth from the year 2020, if I understand that correctly. Some nations signed on, some didn’t. United States did, European nations did, African nations did. But then Russia and India didn’t for competitiveness reasons. Where does this all work in terms of competition? Why would somebody sign on when they’re already possibly not in the best economic situation that compete with other areas.

Ryerson: This is a very timely and I think it’s going to be fascinating to watch this evolve. Basically ICAO came out with a plan for nations to reduce their aviation emissions and different ICAO member states, notably the U.S., the EU, and China signed on. And what they said was that the aircraft that they purchase will have reduced emissions compared to a baseline. It’s very similar to CAFE standards like we have for surface transportation vehicles. That’s how we in the U.S. we regulate the auto industry to help them reduce their emissions and help us as users reduce our emissions. It’s very, very similar. The idea that when the airlines place new orders for aircraft, those aircraft have to be more efficient.

This is something that, at least in the U.S. didn’t seem to have a tremendous amount of airline pushback. In fact, you know, and this is more anecdotal from news reports, but in fact, some environmental groups pushed back and argued that the airlines crafted this legislation and that they were okay with it. But airlines have a tremendous vested interest to reduce their fuel consumption. American Airlines, for example, has this excellent fuel smart program where they’re unbolting anything unnecessary from the aircraft. They throw out the magazines, right? They don’t want an extra pound on that aircraft because they don’t want to consume extra fuel. The airlines want to save fuel. A few years ago, it was 33, 35% of their operating costs. It’s just a tremendous number. And so they want to save fuel and so they want these fuel efficient aircraft. So this will help their competitiveness, or at least let me say, not necessarily harm their competitiveness because they’re looking to adopt new fuel efficient aircraft anyway.

Where I think the ICAO rule might overall increase emissions or not make a particularly large dent in emissions is that aircraft don’t, when a U.S. carrier or European carrier purchases a new aircraft and then they’re done with it, it doesn’t get dismantled and environmentally disposed of. They sell it to another airline, often an international airline, that might be a startup airline or an airline that’s less established and it doesn’t have the cashflow to buy a brand new aircraft from Airbus or Boeing. And so what you find when you track aircraft ownership is that aircrafts don’t go away, they just get passed, and passed, and passed, and then they become a freighter. And then all of a sudden it’s been 40 years and an aircraft is still in operation. And sure it might have new engines and it might have some advancements, but it’s nowhere near as efficient as that brand new aircraft that’s being sold today.

And so while I think you’ll see emissions go down or go down per passenger or passenger mile in the very developed countries, in the countries that signed on to this agreement, you’re still going to continue to see those old aircraft in more developing countries that didn’t sign up. And that’s a part of their competitiveness. Their airlines can’t afford necessarily the new Airbus 350, but they can certainly buy an old Airbus 310 from a carrier that bought it from another carrier previously. I think that is a fascinating open question. How aircraft get passed down and what that means for global emissions.

Stone: Can you tell us a little bit what’s next for you in terms of your research?

Ryerson: My research has always been on this sort of push pull between economic development and competitiveness and environmental concern for the aviation industry. So as far as what’s next one of the first things is this multi-modal network for inner city transportation rather than thinking about airline networks and rail networks and surface transportation. So, right now I’m working on estimating how many auto trips are taken when a small connecting flight between a relatively minor airport in a large airport is canceled. I use the example of Chattanooga, Tennessee before or a Huntsville, Alabama. So as flights have been decreased between those airports and major hubs like Atlanta and other places, how many more autos do we have on the road and what contribution to traffic are those added autos? And I think that linking those two concepts, right? Air service and traffic, really brings together all of the modes of transportation. And so that’s one direction.

Something that we haven’t talked about but is a big component of climate and my research is in adaptation and recovery from climate events in aviation. So, and not just climate events but also acts of terror, something that renders an airport unusable for an extended period of time. How do we divert flights so they’re diverted safely but also diverted in a way that’s passenger centric. If anyone has been on a diverted flight, you can know that that can mean hours and hours and maybe days of disruption to your schedule. How can we divert flights in such a way that we can reaccommodate passengers very quickly. And you could imagine a scenario where airport outages are happening, let’s hope not regularly, but more regularly than they are today. And having a plan for a passenger re-accommodation is going to be a really key part of our resilience. And so this is something that I’m working on, sort of algorithms for climate change adaptation.

Stone: We’ve been speaking with Megan Ryerson, Professor of Transportation at the University of Pennsylvania and collaborator with the Kleinman Center on airline industry research. Megan, thank you for appearing on the show.

Ryerson: Thanks so much, Andy. It was a pleasure.

Stone: Thank you. And thanks to our listeners for tuning in to Energy Policy Now from the Kleinman Center for Energy Policy at the University of Pennsylvania. You can get the latest energy and environment updates from our Twitter feed @kleinmanenergy. Keep up to date on the latest news, research, and events from the Kleinman Center by visiting our website, www.kleinmanenergy.upenn.edu.


Megan Ryerson

UPS Chair of Transportation, Weitzman School
Megan Ryerson is the UPS Chair of Transportation and Associate Chair of City and Regional Planning at the Stuart Weitzman School of Design.

Andy Stone

Energy Policy Now Host and Producer
Andy Stone is producer and host of Energy Policy Now, the Kleinman Center’s podcast series. He previously worked in business planning with PJM Interconnection and was a senior energy reporter at Forbes Magazine.