More mystery shoppers
A flatmate of mine was a BOAC overseas station officer. On one occasion, in between assignments, he was given a multi-sector ticket, out to Hong Kong, back via Seychelles and Nairobi, and told to make sure his baggage was well over the limit, to see how often he was charged excess. He emptied his wardrobe and shoe cupboard into his case and dragged it halfway round the world and back. He never did get charged, but on his very last sector (Rome-London) they lost his bag and he arrived back home with nothing to change into.
On another occasion, in the 1970s, all the clerks and juniors in Market Research were given first-class tickets to all points of the globe and told to report on the usage of the upper deck lounge on the 747. Some poor soul sat up there all the way back from Sydney and the only other punter thay saw was a senior BA manager.