It is worth being precise about what an on board courier is, because the phrase gets used for three different products. It is not a faster parcel service, it is not a premium express label, and it is not a charter. It is a person who buys a seat on a scheduled flight and carries your consignment in the cabin, in their own custody, from the moment they collect it to the moment somebody signs for it.
The other thing being bought is answerability. When a customs officer has a question about a shipment, the shipment cannot answer, so it waits for someone who can. When the question is asked of a courier standing at the counter with the invoice in their hand, it is answered immediately. That is not a marketing claim; it is the entire operational advantage compressed into one sentence.
It is also worth saying what the service does not fix. It does not make a permit appear, it does not make a sanctioned party acceptable, and it does not make an undeclared battery legal. Where those are the problem, a courier only makes the problem arrive faster, which is why the screening happens before the quote.
On the Oslo lane this matters more than average, because the schedule and the customs position both reward preparation and punish improvisation. The half hour spent on the description of the goods before departure is the half day you do not spend at the border afterwards.



