Flight methodology

Travel Impact Model

Google

Google's open model for passenger flight emissions. It estimates each flight from the aircraft type, seat layout, expected load factor and cargo share, and SQUAKE adds Google's contrail rating as a separate indicator.

Publisher: Google
Best for: Comparing flights and reporting with flight-level detail
Result: One total per trip, for all travellers
Energy scope: WTW by default, TTW optional
Non-CO₂ effects: Not in the CO₂e figure; separate contrail rating
Factor year: Not selectable

How it works

By default the result includes producing the fuel (well-to-wheel). Tank-to-wheel is available.

Data tiers

SQUAKE uses the most specific TIM data available for each flight. Each result says which tier it used.

Scheduled flight
TIM's estimate for the scheduled flight, matched by airline, flight number and travel date.
Same flight, historical data
TIM's historical data for the same flight.
Airport pair
Typical emissions for flights between the two airports.
Distance and cabin
TIM's distance-based factors by cabin.
SQUAKE fallback
Used when TIM has no data for the trip.

Contrail rating

Results can include Google's contrail rating. It compares the expected warming from contrails with the flight's CO₂e emissions. It is for information only and is not added to the CO₂e figure.

Negligible: Contrail warming is negligible compared with the flight's CO₂e emissions.
Moderate: Contrail warming is comparable to the flight's CO₂e emissions.
Severe: Contrail warming is higher than the flight's CO₂e emissions.
Unspecified: No rating is available for the flight.

Google advises against converting the rating into CO₂e. Report it next to the emissions figure instead.

Trip details used

When a detail is missing, SQUAKE uses the default.

Detail	Default	Notes
Origin and destination airports	Required	Trips with connections are calculated leg by leg.
Airline, flight number and travel date	None	Needed to match a specific flight.
Cabin class	Economy
Number of travellers	1
Airport emissions	Not included	Can be added, based on Google's suggested average for each airport.
Sustainable aviation fuel	None	A SQUAKE adjustment; TIM itself assumes conventional jet fuel.

What is included

Included

Burning the fuel
Producing and delivering the fuel (on by default)
Airport emissions, if switched on

Not included

Non-CO₂ effects such as contrail cirrus (shown separately as a rating)
Travel to and from the airport

Limitations

Load factors and seat layouts are modelled, so results can differ from the actual flight.

Sources

Google: Travel Impact Model methodologygithub.com
The full open methodology, including the contrail rating.
Google Research: Project Contrailssites.research.google
Background on how contrails form and warm the climate.