Two missiles in cargo hold on Air Serbia flight from Beirut

[surely not]

Safelife you will find x ray scanners at cargo reception points that are capable of scanning freight.

For any really unusually large pieces of freight there are procedures in place for acceptance and to make as certain as possible that it is safe

There are even scanners that can x-ray the freight in situ in the articulated lorries that bring it to the cargo shed.

So whilst I do not have first hand knowledge of the screening available at Beirut, it is not true to say that air freight isn't screened anywhere else.