Boy, Jannie! That's a tough one! I sure do understand your feelings!
Have you talked to him about this? Have you posed some of these questions to him, like still dealing with the public?
Sounds like you may not change his mind, and you're right, he needs to follow his dream, but after talking about it with him, YOU might feel better. A terrorist... well, a bullet can find you almost anywhere nowadays, and since 9/11, there haven't been nearly as many airplane crashes as there used to be... or it seems like it, anyway. They say that flying is the safest way to travel.
At least he's not threatening to learn how to surf at the age of 67, or wanting to learn to fly an ulta-light, or wanting to go skydiving one last time!
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Psalm 119:105 Thy word is a lamp unto my feet, and a light unto my path.