Duo Airways
Working in Vienna approaching Christmas 2003, I booked a flight to Birmingham with Duo Airways. The one-way journey was around £45. The mid-afternoon flight was on one of their Bombardier CRJ700's and upon boarding I was told by a rather bemused cabin attendant that I was the only person on the flight.
Sat way up front in a very comfy seat and enjoyed all I could eat and drink for free for the entire flight. The attendants came and sat with me and chatted about all aspects of the flight including, as I remember, about how they were a bit worried about the passenger loads to Birmingham and, I think, Edinburgh. It was my most memorable flight, most enjoyable!
Unfortunately their fears were not unfounded as the airline ceased trading a few months later, but the memory of my own "private jet" will stay with me forever!