The Airport Coordination Netherlands monitors the conformity of airlines to the allocated slots in cooperation with the relevant authorities. ACNL discovered the non-conformity behaviour of slot usage in Schiphol Airport of the Netherlands, and among nine types of misuses, this paper will discuss the one type of misuses: a flight operated at a significantly different time from the allocated slot. The slot coordination is consist of 5 procedure, the slot allocation, slot monitoring, discussion, enforcement and sanction. Using the exploratory data analysis, the research will explore the different types of behaviour from 5 selected airports, and suggest ways of continuing the monitoring to contribute to the slot monitoring and discussion process.