We don't include an option for business or first class as these classes vastly increase your carbon footprint. The whole point of Lite.Flights is to keep your emissions as low as possible, so we assume you'll be flying Economy.

The CO₂ indicated for each of the search results are based on the following:

• The direct CO₂ produced by the aircraft engines multiplied by

• the indirect climate impact also known as RFI (Radiative Forcing Index). This value varies depending on the aircraft type and the route length and is combination of Nitrogen Oxides (or NOx) and contrail formation. The NOx has a rough RFI value of 0.8 and contrail formation varies from 0.5 to 3.

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We rank every journey against an ideal aircraft. This gives us a baseline against which we compare all results and enables us to rank every search result.

• For journeys under 5000km the ideal aircraft is the Airbus A321 Neo.

• For journeys over 5000km the ideal aircraft is the Airbus A350-1000.

We rank flights using the following system:

• OK: CO₂ must be within 12.5% of the ideal aircraft for the route.

• AVERAGE: CO₂ must be within 25% of the ideal aircraft for the route.

• POOR: CO₂ must be within 50% of the ideal aircraft for the route.

• TERRIBLE: Anything more than 50% CO₂ than the ideal aircraft for the route.

No journey in Lite.Flights is green nor sustainable. There is no currently no such thing as sustainable aviation. There are no electric aircrafts in commercial operation, but we can't wait to see them become a viable option.

Lite.Flights uses the Amadeus flight options API for scheduled airline traffic. It includes around 350 airlines but is currently missing Low Cost Carriers such as Ryanair, EasyJet and Southwest.

We are working to expand our support for more airlines including all LCCs. Stay tuned.

Our database contains an emission and range model for the vast majority of commercial aircrafts. We are constantly working on improving these as they provide the backbone of our ranking system.