Apparently even airplane mode might not necessarily protect you (though I don&#x27;t claim to know how this works in the internals of iOS):<p>&gt; Furthermore while the IMSI is not transmitted often a silent SMS or a failed call will induce the phone to transmit its IMSI or TMSI also in and out of airplane mode while registering on the network.<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Talk%3AIMSI-catcher" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Talk%3AIMSI-catcher</a>