Fly collision detection

Hello

I use ArcMap for load and show DTED data. I'm able to use LLOS (linear line of sight) between two points.
What I want is fly collision detection. It means that if you fly between two points -on a specific elevation-, will you hit a surface or not.
For better understanding, I created this picture:Attachment 23126

I have no idea about how to implement it. If you have, your idea will be appreciated.

By the way, this VB tool is what I want but it uses ArcScene.

Thank you
Sincerely

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