Am looking at the airport activity graphs for JFK. Why does it seem that the number of departures does not equal the number of arrivals over the course of a day or longer time period? The number of departures is much higher.
Probably due to flights ending with cancellation messages instead of arrival messages.
Or Boeing just started a new aircraft factory at JFK. 
I see it with other airports too, where there seems to be a lot of international ops. Could it be related?
Yea, a lot of international flights never “start” so I don’t think we count their arrival on the graphs.