2.1.3. Selection of the key week in the US area
No data were found showing potential traffic variation within a month (i.e. weekly or daily figures).

2.1.4. Data collection period selected
Because obtaining data from parts of the world may be difficult, it was initially decided not to overload data suppliers with overwhelming request but to limit our demand to a day of data collected six times a year. The day of collection chosen was the Friday, generally a busy traffic day. In contrast, Europe and the USA from whom it was easier to get data would supply data for a week (Monday to Sunday). A method was developed to extend the day of data collection for the rest of the world to a week in order to work at the same scale of information. Aware of the fact that contacts for the rest of the world even if successful would not cover the whole world, it was decided to complete the data with Back Aviation database (Phase 2 Paragraph 4).
Table 43 summarises the days of collection. The dates are defined according to UTC time.
Table 43: Timetable for collecting data.

2002  February  April  June  September  October  Decembe r 
Monday  4  8  10  9  7  2 
Tuesday  5  9  11  10  8  3 
Wednesday  6  10  12  11  9  4 
Thursday  7  11  13  12  10  5 
Friday  8  12  14  13  11  6 
Saturday  9  13  15  14  12  7 

Sunday  10  14  16  15  13  8 

2.2. Data requirements
Data required from people to be contacted consisted into two types of information. The first type concerned general flight information such as:
.
Departure and arrival airports.

.
Time of departure and arrival.

.
Callsign.

.
Aircraft type.

The second type of information consisted of 4-D flight trajectories, which includes the latitude, longitude, altitude and time for points along the trajectory.
2.3. Contacts

As an investigation on the data requirement was conducted, aviation authorities that might hold the information were identified in the world. Direct contacts were established for Europe and the USA. Countries of the rest of the world were contacted by e-mail or via a questionnaire.
2.3.1. Direct contacts: Europe, USA
. Europe

The position of Eurocontrol Experimental Centre allowed us to download CFMU flight data for any day directly from a server. European data were obtained for the 6 weeks of data collection. A total of 38 countries were then covered.
. USA, North and Central America

As part of Action Plan 13, an agreement was made between Eurocontrol Experimental Centre and Volpe Center regarding the exchange of North American and European flight data. North American data (mainly USA, Canada, Mexico, UK) were received for the 6 weeks in 2002. 

2.3.2. E-mail contacts: Rest of the world

Contacts found either internally (EEC staff), during foreign delegation visit to EEC, conference or on the World-Wide-Web were followed up by e-mail with Air Traffic Authorities in the world or aviation related authorities. The e-mail included an introduction letter and an overview of the project listing the data to be collected. An example is given in the Appendix. A total of 45 countries were contacted. Very few answered. Positive contacts made led to receiving OAG-type of data from:
　
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