Answer:
The availability heuristic.
Step-by-step explanation:
The availability heuristic is a mental tendecy to name a specific item, object, date, memory, etc, that comes to mind when thinking of a specific event, memory, object, etc. In this case, 9-11 best explains this mental shortcut given that, the first things that comes to mind when thinking of air travel tragedies or terrorist attacks, is that unfortunate incident.