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Colombia for February by e-mail.

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South Africa for September, October and December by e-mail.

Unsuccessful contacts were obtained after exchanges of interesting e-mails with Australia, India, China and Japan.
When no answers were obtained following a first contact by e-mail, a re-launch was done few weeks after. The data required were then reduced to schedule information data. It appears that flight trajectories data were not available very easily and required lots of inputs in terms of human resource and money.

2.3.3. ICAO questionnaire
The involvement of ICAO/CAEP WG4 (International Civil Aviation Organization /Committee on Aviation Environmental Protection) in a study on environmental benefits associated with CNS/ATM initiatives (Communication, Navigation, and Surveillance/Air Traffic Management) revealed to be an opportunity for collaboration. As part of future work to be addressed, ICAO/CAEP WG4 recommended to extend their study to other regions of the world. It appeared that the data required for AERO2K project and by ICAO/CAEP WG4 had a common basis. For this reason, a questionnaire that would serve the purpose of both projects was redrawn. FAA was also involved in the collaboration as member of ICAO/CAEP WG4 and developer of SAGE (System for assessing Aviation’s Global Emissions). A draft questionnaire specifying the type of data required was elaborated and accepted by FAA and EEC; it required the agreement of ICAO/CAEP WG4. Once accepted, the questionnaire should have been distributed to appropriate ICAO regional offices in the world. This would have launched the collection of data with national offices in the world.
This way of proceeding sounded the most appropriate in terms of reaching as many ATC authorities as possible and addressing the request to the right person. Unfortunately the draft questionnaire drawn in collaboration with ICAO/CAEP and the FAA in November 2001 is still in authority to be posted to appropriate ICAO regional offices throughout the world (May 2003).

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3.1. Introduction
The importation of the flight data and the merge of the trajectories produce flight movement inventories that partially represents the annual air traffic in the world. To have a better understanding of the world air traffic for the entire base year requires the estimation of air traffic for all the other days of the year. The flight movement inventories were elaborated from the data that were collected six times a year at different seasons. These six periods of one week correspond to what was called representative weeks made of seven representative days. By opposition, any day for which no data were collected is called a virtual day. To extend the data collected to a full year, a method was developed allowing the creation of an inventory for any virtual day. Virtual days inventories are generated from representative days inventories on which flight movement trends are applied. Trends are derived from the Back Aviation database, which includes information on the distribution of flight frequencies for scheduled commercial operations. Back Aviation database includes only flights scheduled by airlines and so counts less flight than the inventory made for AERO2K, which accounts for unscheduled flights.
3.2. Variables
In a year, the number of flights varies according to the season, the day in the week and the country. These three criteria should be taken into consideration when creating the virtual days.
3.2.1. Seasonal variation
The year was divided into four periods corresponding to the weather seasons in the North Hemisphere such as:
　
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