(Intentionally) blocking the Phone's signal

[jftr]

@therob

But be aware only using it in “flyghtmode” makes sense, because otherwise (every) phone will try to increase sending power to regain contact to the sending antenna of the provider and that would contradict the aim of beeing shielded.

That’s correct but in my experience the shielding (if the bag is properly closed) is strong enough even with increased sending power. That only leaves the battery issue which is certainly a problem.