Xtra Airways here in the US started out as Casino Express, and still primarily focuses on casino junket charters as it's core business.
Back in the 50s and into the early 1960s, several of the casinos in Las Vegas operated their own airlines to shuttle passengers to/from Las Vegas. Hacienda Airlines' was the biggest of the bunch (The Thunderbird Hotel and the Dunes also provided air service as well.) and the Civil Aeronautics Board ended up grounding the casino airlines, which were bringing in more folks into/out of LAS than the commercial airlines were. At it's peak, Hacienda Airlines boasted a 30 a/c fleet that included DC-3s, DC-4s, and Lockheed Constellations.
Such charter services still exist, but the casino operators have a charter airline operating the flights for them. In some cases, the junket operators just buy a block of seats on a scheduled flight to that casino destination.