Assuming such an exploit exists, I don't think I'd be targeted with it. It's my understanding three letter agencies tend to hoard that sort of thing, not blast them at random privacy aficionados.
> the eavesdropping technique "functioned whether the phone was powered on or off."
https://www.cnet.com/news/fbi-taps-cell-phone-mic-as-eavesdr...
I would hope that the FBI would not override airplane mode on a smart phone... what if they did so while a suspect was actually on a plane?
A warrant doesn't give police the right to endanger others IIRC...
Nothing would happen. Just like nothing happens to the thousands of people who forget to switch their phones to airplane mode every day.