Once you say farewell to your bag at the check-in desk and it heads off down the conveyor belt, it's going to pass through a number of hands, with opportunities for pilferage up to and including the time it flops onto a baggage carousel at the other end.
Airlines don't have a clue how many bags are tampered with since thefts don't get reported to them; it's the job of airports to maintain security in baggage handling operations, so they say. Airports do have a clue, but they're not saying since negative reports could only damage their brand.
Insurers are one potential source of information, but their figures are not related to the total number of travellers. Is it 25 thefts from luggage reported per 50,000 passengers or per 5 million? It's only when systematic baggage theft is unmasked that the issue comes to light.
Sting operations conducted in baggage handling areas and anecdotal evidence from passengers point the finger at some of the worst airports, and some of the most astonishing reports come from the US. Not surprising perhaps, since the US alone accounted for almost a third of all the 3.8 billion air passenger movements recorded in 2016.
Theft from passengers' luggage has been an ongoing problem at Johannesburg's OR Tambo Airport for many years, while Manila's Ninoy Aquino International Airport is another happy hunting ground.
The boom area in airline theft involves passengers' carry-ons, caused by fellow passengers thieving from bags stored in overhead luggage compartments. This is a profitable target since laptops, cameras, jewellery and wallets are likely to be stashed in carry-on bags.