> Ultimately I'm just not satisfied with any estimate of CO2 emitted by flying in general. > Has anyone here seen a decent model of CO2 output caused by flying

> Ultimately I'm just not satisfied with any estimate of CO2 emitted by flying in general. > Has anyone here seen a decent model of CO2 output caused by flying? The CO2 impact of flying, and of flying first-class, is understood incredibly well and quite simple to follow for first-order effects. First, to calculate the emissions associated with the sector as a whole, you don't need any modeling. If you know how much of what fuel the sector as a whole consumes, you can determine co2 emissions directly from that fact. That's how those broader statistics are determined. Second, losing one passenger impacts the fuel economy per person in a very negative way. Consider an Airbus A321, which is one of the more efficient commercial airplanes. Wikipedia states that its max takeoff weight is 93,000kg. Suppose it's configured to seat 220 people. That means 422kg of weight being transported per person. A typical airline seat weighs 11kg and an average adult is over 70kg. If you assume an average of 50kg per person for luggage, each person's marginal contribution to the weight being transported is 131kg. The rest is coming from moving the plane itself. So, if you replace two small seats with one big one, that one seat now goes from having a share of 422kg to (422 * 2 - 131) = 713kg. That's an increase of 69%. Edit: I realized I'm looking at max capacity for total weight but not max weights per passenger, which means my guess of the plane weight is overstated. But I also didn't account for the fact that first class also requires more flight attendants on the flight. These two things counter each other. The net increase is likely something other than 69%, but that's not too far off. Yes, there are other market impacts from using first class, but there's no basis for thinking those are anywhere close to the impact described above. (E.g., you can do the calculations for offsetting 50kg of cargo from another plane.) What's a little less certain is the impact of radiative forcing. CO2 emissions are a dangerously _understated_ way to think about climate impacts of flying. CO2e (co2 equivalent) is more relevant. When you release water vapor, NOx, etc. into the atmosphere at higher elevations, there are all sorts of other impacts that occur at different timescales. The IPCC recommends multiplying by a factor of 2.7x to account for that. Other studies are a bit lower, maybe 1.9x, but there's general agreement that it's very bad. The specifics still need to be understood a bit better. People have incredible wishful thinking when it comes to flying because it's so convenient. It is impossible to act responsibly towards the environment and engage in air travel with any form of technology that exists today or that we know of. It's hard to imagine many things more hypocritical than first-class passengers who also claim environmental concern.