I remember reading that (some?) phones in airplane mode can still be pinged by the network to request their location and the call is answered directly by the blackbox modem rather than by Android/iOS bypassing most privacy features.

Airplane mode also usually keeps Bluetooth and WiFi enabled so that's one thing to look for.

Airplane mode usually turns off the power to that chip.

I found this for GrapheneOS / Pixel devices which seems to support this claim: https://grapheneos.org/faq

> Activating airplane mode will fully disable the cellular radio transmit and receive capabilities

I am very interested if you have more information on this or specification on whether airplane mode has to disable power to the chip.

There’s always Faraday cage bags for cell phones

Yeah, they don't work though. They're about as effective as those signal-boosting stickers you could get at truck stops in the 00s.

Really? I used to have one and it always killed my battery looking for signal. It also prevented me from making calls to the phone.