The really big question of course is whether a preemptive strike can be made against Iran. The difficulty there is that any attacking aircraft would have to transit Iraq or Syria. Now that the USA has withdrawn from Iraq, that route has become less certain.Syria would have been an option IF the Arab League & Turkey had managed to impose a UN no-fly zone over Syria. However Russia effectively vetoed that idea.
So any attacking aircraft may have to fight their way in, and back out again.