0.5mg Klonopin = 0.5mg Xanax (alprazolam) = 0.5mg Ativan in terms of strength? Which is "best" for fear for flying/claustrophobia on airplane? I can't tell.

No. Those equivalences dont' work. But you should be speaking about this with your prescriber, who knows you and your particular fear of flying, as well as your medication history and your need for length of medication action.