Book-and-claim
Book-and-claim is an accounting system that separates the environmental benefit of sustainable aviation fuel from its physical delivery. A customer pays for SAF to be produced and put into the fuel system at an airport where it is available, say Los Angeles or Amsterdam, and claims the emissions reduction for a flight departing somewhere with no SAF supply. It solves the logistical problem that SAF exists at only a handful of airports and avoids trucking fuel around, which would itself generate emissions. Credible schemes use a registry to prevent the same litre being claimed twice; ask which registry an operator's SAF programme uses before paying a premium.