For my part, I contribute what I know in these fields. On the air side, they use it for very small quantities, maximum 10kg or so, and it is also a logistical nightmare and there are many variables, customs dogs and the same person who is responsible.
Now with cargo planes there are specific cases in cargo planes after passing the controls and after passing all the controls having people at the airport and in the company you can have an inspection by the airline security itself, arrive and force them to unload the goods to check that they do not introduce Cocaine into them. By boat it is slower but more effective. Here there are several. One of these methods is to do it with surprise, that is, a company container is opened and rewarded. It is loaded with suitcases of 20 to 25 kg and normally they are 300 to 500 kg maximum. more than anything because if you have only achieved departure then at the port of arrival you have to have the contact to know if that container is going to inspection, they are 3 colors orange, green and red, another factor also plays here, there are too many containers arriving on the same ship and it is totally impossible to inspect them all, therefore this is the most used modality at the maritime level apart from all the many others that there are. But even so, we must keep in mind that some cranes can detect the overweight of the container, so that draws attention. It is easier to detect from 500 than from 300. For example, it takes 300 to prepare the truck to enter and remove the suitcases and leave the port.
On the other hand, there is a rumor that containers that are fully paid for are loaded and unloaded normally like any other, but here we are already talking about quantities of 1 to 10 tons. The truth is, I don't know if this exists or not, but surely paying the right, very right people. Those lines really exist.
That is why I prefer distribution already at destination at a good wholesale price (if anyone has stock in Spain I would be interested) In conclusion, it is always better to ship by sea for large quantities since it is impossible to handle large quantities by plane. This is a very extensive topic that can be talked about at great length. I hope you like my information, greetings to all