Comment by Xixi

"Under TotalCare, an airline pays Rolls-Royce a fixed rate per engine flying hour." [0] Not quite kN-h indeed. But the idea is similar (and more simple to implement, I suppose): you don't really own the engine, you pay for what you use.

[0] https://www.meritshot.com/rolls-royce-case-study

EDIT: wording