Lite.Flights is a carbon conscious flight search engine. What we mean by that is that at the core of our product is a comparison of aircraft types and their carbon footprint over a given route. This data is based on a variety of publicly available emission information.

In our database we have over 70 aircraft types. These range from regional jets such as the Embraer 175 all the way to the A380-800 and almost all types in-between.

We have created detailed emission models for these aircraft over various distances. This allows us to recommend what we believe is the best aircraft for any given route. We call this the ideal aircraft.

Our route database covers most of the world and includes the majority of the world's airlines with some notable exceptions.

At present we do not have data on Ryanair, EasyJet and other Low Cost Carriers (LCCs). This is something we are active working to add and is due to a limitation by our current data provider.

A search result provides us with a departure & arrival airport, airline, the IATA code for the aircraft type assigned to that route and a whole lot more. The IATA code for the aircraft type is the data point we are really interested in, because it allows us to rank the flight on the route from Ok to Terrible.

As there are no sustainable aircraft types in operation today, we are reserving the use of terms such as Green and Greenest for the future when they come into service, which is some way off.

Sometimes the iata code is vague and gives a family of aircraft, in which case we use the most common type.

Airlines assign an aircraft type for a given route a long time in advance. Ticket sales are based around the number of seats available and this is also what our search results are based on.

In the real world things change, sometimes quickly. Airlines will often have to assign a different aircraft for a route with little or no notice given. This could happen for any number of reasons such as:

• An increased interest in the route meaning the airline assigns a bigger aircraft (or smaller if the interest is smaller than anticipated)

• The aircraft goes tech (needs repair).

A good example would be Aeromexico assigning their Boeing 737-800 instead of the Boeing 737-8 MAX for the Cancun - Mexico City route. The two aircrafts are essentially interchangeable from a seat count point of view, but have very different emission profiles.

As a passenger with a ticket in your hand and about to board, you will have little choice at this juncture.