About 30 years ago CP Air used to have several specially outfitted and painted 737s that flew only business class in the entire plane (only 5% premium over full fare). They folded down the center seats and everyone had a window or aisle - no kids allowed. The service was called Attaché.
The plane could be used for "regular" flights by raising the center seatbacks. The flight attendants were also specially trained and the service on those flights was excellent, as was the food and drink. During my "working" years I flew a lot and was able to fly Attaché quite a few times until the service ended. Those were the days!