For posterity, I'll add that I'm impressed at how quickly the AI seemed to learn its lesson after I bloodied its nose with Air Intercept. It's now exclusively targeting areas I can't reach even if they're suboptimal to hit. I'm disappointed in how the AI isn't really ramping up the air war and ...

It works! Building an airbase closer, but not right on top of the front line brought the combat within interception range, which I suppose is 66% as you suggested. Thanks for the idea.

Interesting, I read that but assumed the action points would only affect combat endurance but not range. The distance is just over 66% - maybe that's the problem. I will try relocating the airbase or developing a longer range fighter to test this hypothesis. Thank you!

I'm being hit by level bombers every turn. I have fighters and fighter-bombers with "air intercept" set in their unit settings and maximum readiness. The bombing of my troops is happening within their range (it's seven tiles away, their range is nine tiles). But I never get a successful interception ...