4D contracts strategic planning

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Several months before the actual date of the flights, the 4D contracts of all the aircraft are generated. These 4D contracts are conflict-free, i.e. all the contract bubbles are not intersecting at any time. In order to ensure this characteristics, the size of the contract bubbles vary along the flight, according to the local traffic density.

The 4D contract concept can be summarized as: as long as all aircraft respect their assigned 4D contract, the overall system is safe and predictible. This operationaly translates as: as long as all aircraft remain within their assigned contract bubbles, no action is required.

Of course, many situations can lead to trajectory modification implying a risk of 4D contract break. In this case, a 4D contract update process is triggered.

This video illustrates this strategic planning: only contract bubbles are represented.

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The 4D contract concept
Last update Wednesday 30 October 2013