My mother ran a travel agency for over 20 years just for that purpose. She did many millions in ticket sales a year, at one point had a staff of about 20. To get to the rich stuff, she had to become IATA certified and get a IATA number, (which implied a certain sales amount in the multiple millions USD). I don't think she ever made any serious money at it after all expenses, but she got many, many perks. Free incentive trips, walk-in upgrades to F, deep discount tickets for herself and my father (and sometimes her family), great hotel rooms. When you throw that in, it was an incredible deal. And it kept her busy and out of trouble.

As airlines began getting stingier with commissions, and the onslaught of DIY travel and the internet, the losses piled up, with a severe curtailment of benefits, so she eventually threw in the towel. But it was a good run.