Well, isn't the AirTag essentially a bluetooth device, whereas the iPhone's "Find My Plane/Phone" is based on GPS? So if the plane goes down in a rural area the AirTag won't be very effective unless they sweep the area?
I have bone conductive headphones for swimming, they have to have a built in MP3 player as even slight immersion in water will block low power BT. They start to pause as the buffer can't keep up.