These estimates are made by combining multiple sources of data and applying our knowledge and experience.

We have a well-defined methodology which has improved over time:

T2RL track the number of passengers boarded for each airline every year. We also adjust this passenger number to include franchise partners. We then work through a combination of publicly available data and our own sources to develop a perspective on the split between direct and indirect channels. We focus on gathering information about bookings made via airline's websites, call-centres, direct connect channels, host direct and GDS.

We regularly conduct interviews, both formal and informal, to validate our hypotheses with airline executives and the providers of technology solutions to airlines.

We are also permanently active in the travel industry and IT and distribution market by providing information and consulting to airlines and other travel providers around the World.

We combine these components to develop a perspective on the split by channel and make our estimates.

We have established the following definitions for each channel:

Channel	Passengers Included
Web	Passengers buying tickets on the airline.com site. Today the vast majority are leisure consumers and unmanaged business travellers. For the moment this also includes mobile.
Call Centre and ATO/CTO	Passenger sales or tickets created by airline employees or airline contracted third-parties working from call-centres, airport ticket offices and city ticket offices.
Tour Operator	Passenger sales through a block allocation of inventory to travel agents or tour operators. In particular those made by Vertically Integrated Tour Operators (VITOs).
Global Distribution System	Flown passengers sold via the Global Distribution Systems (GDS). These are currently defined as Amadeus, Sabre (including Abacus from 2015) and Travelport. GDSs are characterised as having travel agency subscribers and offering the ability to sell multiple airlines in one system.
Host Direct	Flown passengers sold via the local Computer Reservation Systems (CRS) providers. These are known as Axess, Infini, Sirena, Topas (until 2013) and Travelsky. They are typically used in home markets to sell a select few number of home based airlines.
Direct Connect	Passenger sales sold via channels with a direct connection/API/using NDC messaging standards direct to the airline system. These are mainly used by LCCs to connect to Online Travel Agencies, but some airlines also use direct connect in their strategy to offer content direct to corporate booking tools, agency portals and metasearchers.

Clearly each airline has its own strategy and approach to distribution. Boundaries between the channels are becoming more and more blurred from a systems perspective.

We constantly strive to improve our estimates and modelling to get the right information to our Subscribers. We have undertaken a number of initiatives to test different techniques and modelling practices and have sponsored academic projects at the London School of Economics. We strive to establish a Worldview of Distribution for the airline industry. We believe that the solution lies in combining information about consumer behaviour, airline offerings (schedule) and existing market shares to present and project changes in the distribution landscape. Our work is currently academic in nature and largely mathematical. We are committed to developing our Worldview for the future to improve understanding of this challenging area.