Direct Operating Cost (DOC)

Direct Operating Cost is the variable, per-flight-hour cost of operating an aircraft — fuel, engine and airframe maintenance reserves, and landing/handling fees. It excludes fixed costs like crew, insurance and hangar. DOC per hour is the number most often compared between aircraft, but the fully-burdened cost (fixed + variable ÷ hours) is what actually hits an owner.

Why it matters: DOC is the hourly cost that scales with flying — fuel, maintenance accruals, engine reserves, landing and handling. It is the number that answers what one more hour costs, which is the right lens for pricing a trip, comparing types at the margin, or deciding whether to reposition.

The trap is comparing DOC figures that include different things: one source's number includes engine reserves and another's does not, one assumes cheap fuel, another dear. Fixed costs — crew, hangar, insurance — sit outside DOC entirely, which is why an aircraft's total hourly cost at low utilisation dwarfs its quoted DOC. Always ask what is inside the number.