Might have triggered: SFO near miss happened, either it's unknown whether the aviation disaster happened (but there are suspicions it did), or it's unknown whether the two events were related (but there are suspicions they are).
Would have triggered: SFO near miss did not happen, but if it had happened, it would have triggered the aviation disaster.
Could have triggered: SFO near miss did happen, but there was no aviation disaster, though there could easily have been one if it hadn't been actively averted.
> Could and might are often, but not always, interchangeable. He might have come / studied = 'We don’t know whether has come / studied or not', but you could substitute could. If you want to indicate ability or permission, however, you need He could have come / studied = ‘He had the ability to come / study.'
> It's possible that he came from a different culture would be used in considering a historical figure who didn’t seem to fit into his environment. If you were talking about a current situation, you’d say It's possible that he comes from a different culture. It’s hard to think of any circumstances in which It's possible that he come from a different culture would be used, even if you regard ‘come’ as subjunctive.
> English modal verbs are both important and subtle. You're unlikely to gain a full understanding of their use in exchanges such as this and if, as I assume, Noah, you are a non-native speaker of English you really need the help of a qualified English teacher.
