a 737 in from Lithuanian was needed in Italy, but, there was only one guy in Lithuanian that wanted to fly to Italy to defray the cost of flying it there...

the plane with a capacity of 189 passenger seats only had 2 pilots, five crew members, and 1 passenger.

Tour operator Novaturas confirmed to CNN Travel they chartered a flight from Bergamo to Vilnius for a group of clients that day. In order to avoid the aircraft coming back empty, one-way tickets were put on sale for the return trip.

Strimaitis says the pilot referred to him as "Mr Passenger" while speaking over the tannoy after the plane landed at Orio al Serio International Airport in Bergamo. "The crew said how nice it was to have me on the board," he explains. "I'm sure it was an easy job for them."

https://www.cnn.com/travel/article/this-man-was-the-only-passenger-on-a-boeing-737-to-italy/index.html
https://www.scmp.com/news/world/europe/article/3004385/7-crew-1-passenger-lithuanian-man-flies-alone-boeing-737-italy