ATFM slot adherence
ATFM departure slots are allocated centrally by the Network Manager to hold aircraft on the ground when there is an envisaged imbalance between demand and capacity at airports or en-route.
ATFM slot adherence measures the share of take-offs outside the allocated ATFM window. Within the EU, the monitoring of ATFM slot adherence is required by Regulation (European Commission 2010). ATS units are required to provide information on non-compliance for airports where non-adherence equals or exceeds 20% of regulated departures.
European Commission. 2010. “Commission Regulation (EU) No 255/2010 of 25 March 2010 Laying down Common Rules on Air Traffic Flow Management (Text with Eea Relevance).” https://goo.gl/cPbYDQ.