When you board a massive commercial airliner, it is highly likely that the airline does not actually own the engines bolted to the wings. Over the last few decades, manufacturing giants like Rolls-Royce and GE quietly stopped selling their multi-million-dollar turbines outright, pivoting to a radical, highly lucrative subscription model known as "Power-by-the-Hour." In this B2B arrangement, airlines lease the engines and pay a flat fee solely for the hours the turbines are physically generating thrust in the air. This book dissects the staggering financial engineering behind modern aviation leasing. We explore how this model forces manufacturers to obsessively monitor their engines via live telemetry, turning them from simple hardware companies into proactive, data-driven maintenance monopolies. The narrative exposes the hidden cash flows of international aviation, demonstrating how standardizing maintenance completely eradicated the aftermarket parts industry and locked airlines into unbreakable, lifelong corporate contracts. Look beneath the wings of global travel. Understand the brilliant, recurring-revenue subscription model that completely dominates the modern aerospace economy.