Grizz...
There is nothing that 'triggers' ai. All ai aircraft fly fixed schedule(s) as defined in the 'traffic*.bgl' file. If you're not there at the right time the ai will just sit there until their departure time.
Assuming the aircraft you're seeing are ai, not static scenery objects, and that the airport meets the requirements for ai operation, they will depart/arrive at their scheduled time. If the airport does not comply, the ai will simply disappear at departure time.
From your system specs I'll guess you're running FSX. If you have the SDK installed you can activate the Traffic Toolbox. This will give you the Traffic Toolbox Explorer under the
Tools menu. The Explorer
At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation.