Comment by Terr_
From what I can find, the targeted pager-model can receive UHF messages in the 450~470MHz range. That could reach passenger jet cruise altitudes if the transmitter is strong enough.
I think it's safest to assume Hezbollah are using strong transmitters, because they'll want to be able to broadcast across rather large areas and in a way that resists potential jamming.
On the flip side, I'm having a hard time imagining these as threats to an entire airplane, given the tight constraints on how much explosive power can be secretly snuck into a functioning pager.
Penetration of 450-480MHz through the shell of an airplane would, on the ground,require a transmission strength of approximately .4dB/m at a distance of 1 kilometer, which is doable by most measures, but would quickly become unrealistic as the plane gained altitude.
https://pure.tue.nl/ws/files/68269081/560768.pdf