The private aviation glossary
104 terms explained in plain English — from ACMI to wet lease.
B
Book-and-claim sustainability
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.
C
Carbon offset sustainability
A carbon offset is a credit representing one tonne of CO2 avoided or removed elsewhere, such as through forest protection, methane capture or direct air capture, which a flyer buys to compensate for a flight's emissions. Offsets are cheap relative to a charter, often $10–$50 per tonne against a light jet's roughly one tonne per flight hour, and many operators bundle them into the price. Quality varies enormously; many avoidance credits have been shown to overstate their benefit, so look for verification under Verra, Gold Standard or similar, recent vintages and preferably removals rather than avoidance. Offsets are a complement to flying less and using SAF, not a substitute.
CORSIA sustainability
The Carbon Offsetting and Reduction Scheme for International Aviation is the ICAO programme under which airlines and large operators must offset growth in CO2 from international flights above a 2019 baseline. It became mandatory for participating states in 2027 after a voluntary phase. Business aviation is largely exempt because the scheme only applies to operators emitting more than 10,000 tonnes a year on international routes, but big charter fleets and fractional providers do fall within it, and their offset costs filter into pricing. CORSIA's importance for the sector is mostly indirect: it defines which offsets and SAF count as eligible, a standard many corporate flyers now use for their own reporting.
E
ETS (Emissions Trading System) sustainability
The EU Emissions Trading System requires operators of flights within the European Economic Area, plus flights to Switzerland and the UK, to surrender one allowance for every tonne of CO2 emitted; the UK runs a parallel scheme. Small emitters below 1,000 tonnes a year on non-commercial flights are exempt, but charter operators and larger private flight departments are not, and with allowances trading at €60–€100 a tonne, a two-hour intra-European flight on a midsize jet carries an ETS cost of a few hundred euros that appears in the quote. Free allowances for aviation are being phased out entirely, so the line item will keep growing.
S
SAF (sustainable aviation fuel) sustainability
Sustainable aviation fuel is jet fuel made from non-fossil feedstocks such as used cooking oil, agricultural waste or, eventually, captured carbon and green hydrogen. It is chemically similar enough to be blended with conventional kerosene, currently up to 50%, and needs no engine changes, cutting lifecycle CO2 by 60–80% depending on the pathway. Supply is tiny and it costs two to five times as much as regular fuel. In the EU the ReFuelEU regulation obliges fuel suppliers to blend 2% SAF from 2025 rising to 6% in 2030, and the UK has a similar mandate, so European charters already carry a small SAF cost. Operators sell voluntary SAF top-ups, often via book-and-claim.