@wassim831
The amount of traffic generated at airports can be controlled by the "Time Before Departure Value (Mins)" option on the Traffic Control Centre > Options page.
By default, this value is set to 90 minutes which means from the time you load a flight, the next 90 minutes of departures will be generated at the airport.
If you wish to increase the amount of traffic generated, increase this value. If you wish to reduce the amount of traffic generated, reduce this value.
Note: Any changes in the Traffic Control Centre will take effect the next time the simulator is launched.
Hope that helps.
Mark - Just Flight