Where does Google get this information?
Each estimate comes from one of two trusted sources. Beginning in July 2025, whenever available, we use the EASA Flight Emissions Label, which is based on an airline's own verified historical data for a specific route. The EASA label is a voluntary standard that some airlines integrate with to provide standardized emissions estimates to consumers.
Otherwise, we use our Google Travel Impact Model (TIM). The TIM is administered by Google and overseen by an advisory committee of leading experts in sustainability and aviation. It provides detailed estimates by using a sophisticated model that combines public and licensed datasets with the latest science and internationally-recognized standards.
EASA and TIM have committed to align their methodology so that users can fairly compare estimates from each. Estimated reductions from Sustainable Aviation Fuel (SAF) that are reported by EASA are not included in the CO2e estimate and are shown separately. This information is available in a tooltip next to the estimate.
To learn more, check the:
Lifecycle emissions
The Travel Impact Model accounts for the full lifecycle of jet fuel emissions by estimating well-to-wake emissions. Well-to-wake emissions are the sum of emissions produced by making and transporting jet fuel, as well as the carbon emissions (CO2) from burning fuel during take-off, cruising, and landing.
In addition to CO2, the TIM converts non-CO2 emissions into their "CO2 equivalent" (CO2e) on the basis of their global-warming potential.
Typical emissions
Typical emissions are calculated following the Typical Flights Emissions methodology which estimates the median emissions for your searched route.
Emission estimates for each flight are compared to the route's Typical Flight Emissions. This is how Google identifies flights with higher, typical, or lower emissions.
For some searches, you may find no "lower emissions" flights. This happens when the flights on your searched dates aren’t less polluting than the route's Typical Flight Emissions. To find lower emission flights, try different dates or consider other airports nearby.
Unknown emissions
Factors impacting emissions
Actual emissions might vary and depend on factors such as:
- Aircraft model and configuration
- Speed and altitude of the aircraft
- Distance between origin and destination
- The number of passengers
- The amount of cargo carried
To understand the emission estimates that we display, it's important to know:
- Non-stop flights aren't always less polluting, especially for long routes. It's possible for a multi-stop flight on fuel-efficient aircraft to emit less than the non-stop option.
- Aircraft with a similar capacity and range can have very different emissions. Contributing factors include the aircraft type, or the seating layout used by the airline.
- For flights to, from, and within the US, the model estimates passenger load factors using historical data from the US Department of Transportation. For flights outside the US, we use historical load factor data provided by ch-aviation when available. For all other flights, emission estimates consider a 2019 (pre-Coronavirus pandemic (COVID-19)) industry average load factor.
- Our emission estimates don't yet consider factors such as direction of flight or the use of sustainable aviation fuel.
- Details on the data sources, and on how we combine and use them to derive emissions estimates found in our GitHub documentation.
Other warming effects of flying
In addition to releasing CO₂ into the atmosphere, flying causes other warming effects, most notably through contrails.
Condensation trails (contrails) form when an aircraft flies through regions of high humidity. Water vapor in the air condenses around tiny soot particles in the aircraft’s exhaust and then freezes, forming line-shaped cloud trails.
Most contrails dissipate quickly, but for a small fraction of flights, atmospheric conditions align to produce contrails that persist and spread out, trapping heat in the atmosphere. These persistent contrails account for about a third of aviation’s total warming impact, making the full climate effect from flying substantially higher than fuel-based CO₂ estimates alone.[Lee, 2021. CO2e/GWP100].
Predicting and attributing contrail warming potential to single flights at the time of booking is difficult. This is because weather and atmospheric conditions are hard to forecast accurately in advance and most contrail warming impact comes from only a small number of flights. However, Google has partnered with leading scientists and aviation experts to develop flight-level contrail impact models. This makes it possible to surface these estimates directly in Google Flights.
Each flight on Google Flights includes a contrail impact estimate, visible in the flight details. This shows the potential predicted warming effect of contrails relative to the flight’s estimated CO₂ emissions. The estimates are organized into 3 categories:
|
Category |
Estimated Contrail warming potential additional to fuel burn impact |
|---|---|
|
Low |
Up to 20% more impact |
|
Medium |
20-100% more impact |
|
High |
Over 100% more impact |
Keep in mind: These indicators are predictions based on historical weather data. Actual contrail formation and warming impact can vary depending on the specific atmospheric conditions at the time of flight.
Train emission estimates
To calculate emissions for trains, Google uses a method that considers the kilometers traveled and the number of passengers in your search. Trains emit 19 grams CO2e lifecycle emissions per passenger kilometer on average, according to the IEA. Exact emissions depend on the train and operator. IEA’s data is updated annually and Google is working to source accurate information from train operators.