I believe that the Israeli's can definitely trust the Saudi's to allow the Israeli pilots to fly over Saudi Arabia on their mission to Iran. Now let's say the Israeli's are foolish to trust Saudi Arabia? What would Saudi Arabia do once the Israeli jets are flying over Saudi Arabia? Would they shoot them down, is that the idea? In other words, what harm can come to Israel if they believe Saudi Arabia when Saudi Arabia gives them the okay to fly over their country? I mean, wouldn't the Saudi's have more to fear from Israel at that point?
As has been pointed out, the Israeli's are doing Saudi Arabia a very big favor by taking out Iran's nuclear sites, so they will be more than happy to allow Israel to do it.
That's how I see it anyway.