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A few of those might accidentally shake loose when you pass well known tourist locations...

Terrorists don't need to know which plane they shoot down. Just pick a big one.

Assassins don't want to kill hundreds of people as collateral damage because they don't want to motivate law enfocement more than absolutely necessary.

There is no reason to use this app for targeting planes.

Simple solution:

Use one time pad encryption.
Hand out the key that produces the desired plaintext.

This law isn't to prevent you from taking pictures. Its to make it harder to take pictures with a very specific class of devices without being noticed.

The problem with this approach is that cell phone cameras are improving in quality. In a few years they will be good enough that many people will want to use them as their only camera.

Now imagine a wedding ceremony with 200 beeping cameras.