Nuclear Bomber question

I was trying to nuke a big group of 95 units. This player had right of way trough an AI country, so I figured I could attack the 1 militie that was standing in the AI province. The group of 95 units was 30 seconds away from the dot when my bomber would of completed its attack but it got destroyed. I was surprised that the anti air units of the 95 group was able to destroy it since I was not attacking it and it was 30 seconds away from the dot.

For future strategies is there a magic distance where the AA from my enemy wont do damage to my bomber but still get splash damage from attacking the 1 militie that was standing in the province?