This page is for those of you who want to know the details of where our numbers come from and what they mean. There are many topics. We've tried to order them from more significant to more esoteric.
Why are FlyBetter's CO2e numbers roughly double Google Flights.
Unfortunately the warming impact of flights is not just limited to the emissions of the aircraft. Persistent aircraft contrails (the long thin clouds aircraft leave behind) can have very significant warming effects. Especially at night these clouds produced by aircraft trap heat. The amount of this contrail warming potential can vary significantly and can even depend on atmospheric conditions.
You can read why the Travel Impact Model that Google Flights uses has chosen to leave contrail warming out of their emissions here.
Because FlyBetter compares ground transportation with flying we have to at least approximately include this contrail warming effect. If we don't, our comparisons would be very skewed. A standard method of including this effect is to multiply the CO2e number by a factor. We are using a relatively small warming factor of 2.0. This means that if a flight is modeled to have released 100 kgs of CO2_e greenhouse gasses for a particular itinerary, the warming effect of that trip becomes 200 kgs of CO2_e once the additional warming is added in. This figure comes from the Sustainability Indicator Management & Analysis Platform (SIMAP). We have chosen to use something close to the 1.9 factor used by DEFRA rather than the higher 2.7 factor from the IPCC.
If you want to add another deeper layer to your flying green credentials, you can pay attention to this information box and choose flights with lower contrail warming potential. The organization Blue-Lines is working on reducing this source of warming.
What exactly do the "Travel Modes" map to?
To keep the site simple we have chosen a couple of canonical types of travel. The table below summarizes what each of the travel modes means.
| Travel Mode | Description |
|---|---|
| Average Jet | Boeing 737 for ranges up to 4000 Nautical Miles Boeing 747 for ranges from 4000 to 7500 Nautical Miles |
| Modern Jet (efficient) | Boeing 737-Max for ranges up to 4000 Nautical Miles Boeing 787 for ranges from 4000 to 7500 Nautical Miles |
| Regional Jet (inefficient) | Embraer E170 Valid up to a range of 2000 Nautical Miles |
| Average Car | 25 mpg (eg Toyota Highlander) |
| Efficient Car | 40 mpg (eg Toyota Prius V) |
| Inefficient Car | 16 mpg (eg Toyota Sequoia) |
Why haven't you included electric cars?
We do plan on including electric cars in the future, but unfortunately their warming effects are difficult to include in our current relatively simple warming model.
Typically the warming impact of driving an electric vehicle is lower than driving a gas powered vehicle, but it is still quite substantial. The challenge of modeling electric vehicles is that a substantial portion of their lifetime warming impact occurs at the time of manufacture and less impact occurs during their operation. To create a valid equivalency between electric and gasoline powered vehicles we would have to model the warming impact of their manufacture. And then if we created a more sophisticated vehicle warming model that includes manufacture we would also then have to model the warming impact of the construction of aircraft. We are currently not up to that level of modeling complexity.
So what is your current model?
We believe Google's Travalyst impact model to be quite good in most aspects. We mainly follow this model using the following simplifications
- We limit the choice of aircraft to a couple of distinct types.
- We don't customize loading and load factor to the specific flight. Instead a user can customize this.
- Instead of using seating class factors from IATA RP 1726, we used United and Luftansa aircraft configurations from seat guru. (Listed below.)
We added radiative forcing to our model to allow for better comparisons between flying and driving.
Seat Guru links used in our model
In updating this website for launch in April 2026 we realized that SeatGuru is out of business and we did not archive these pages so these links and this information is currently broken. We apologize that this doesn't meet our bar of full transparency. We will work to fix this shortly after launch. Until then trust us that the data is reliable from actual aircraft configurations.