The carbon friendly flight finder is a joint initiative from Global Travel Market and The Carbon Consultancy to help support carbon efficient travel choices. This is how it works.

The carbon emissions from flying result from the amount of fuel burned during a flight. Like a car, each plane will burn fuel differently and this will depend on a range of factors of which weight is a major one. Your impact on the environment when you fly will depend heavily upon the plane type, how full it is, how many available seats it has and a number of performance factors over which you have no control. What you can control is your choice of provider based upon the efficiency of the equipment they use. Basing your choice of flight on relative carbon impact will help to alter demand patterns for air travel and deliver greater efficiency from flying.

Until airlines provide exact fuel consumption against flown passengers you will not be able to make a choice based upon actual efficiency per plane per airline, so for now the best that can be done is to use available data to help make your flight choice more informed. The carbon friendly flight finder uses the published long haul fleets of individual airlines, EU aircraft fuel consumption data and UK government fuel to emissions conversion values to assess each plane's overall emissions footprint.

The total plane footprint is then divided by the published manufacturers 2 class seating configuration for long haul and 1 class seating for short haul, to provide an optimised emissions estimate per available seat/per plane value. All the relevant aircraft in an airline fleet and their seat values are multiplied to create a fleet value, with a separate analysis for short haul and long haul fleets.

Your flight selection is assessed for distance to determine short haul and long haul fleet selection. The total short/long haul fleet value is divided by the number of planes of each type, to give you a weighted average of seat value across a fleet. We have then organised these to provide an indication of the most carbon friendly airline choices. This means that the carbon rating of the airline links to both the statistical probability of the plane types you will travel on when flying and aircraft performance.

When you use a GTM flight search we do not know which actual plane you are flying on or how full I will actually be, so the best suggested choice we can give you is fleet based. We would like to give you a rating per airline based upon more extensive available data, including class and routing, but this would take a long time for each search to populate. If you would like more information on this please visit our partner site www.carbonresponsible.com where you can learn more about travel and flying emissions stuff.

If you have a choice when you book, always fly direct, the impact of an indirect flight choice can have a carbon impact up to 29% that of a direct one, more if you stop at more than one city en route. This means that any direct flight suggestion we give you will be normally be outweighed by the selection of an indirect flight.

Economy flight is less carbon intensive than business or first class and the fewer seats that your chosen airline put on an aircraft may increase comfort, but increase the likely impact from your journey, making a long haul two class plane more efficient per passenger than a four class plane of the same type.