The longest regular non-stop commerical flight is an interesting case study in business design. For a flight to be profitable it has to balance supply and demand at the right price. For long-haul, direct flights this particularly means balancing distance (providing convenience) and weight (due to fuel and passengers) and cost (mix of premium and economy seating).
And so, how do you get a commercial airliner to fly further than any other to create a new long-haul direct flight? You limit the number of passengers so it can take on more fuel and then you sell those limited seats at a higher price for what’s now an exclusive service.
Singapore airlines flight 21 from Newark to Singapore is currently the longest non-stop flight* at ~9,500 miles and does just this: it contains only 104 business-class seats, reducing passenger weight and thereby enabling it to take on more fuel. This creates a premium service for the select group of passengers willing to pay for it. Great example of how business models can be designed to create new relationships between customers and providers.