The short answer
TBO is time between overhauls — the manufacturer's recommended hour (and sometimes calendar) interval at which an engine should be overhauled. It matters because an engine's time relative to TBO is one of the biggest drivers of an aircraft's value and financeability: a mid-time engine is far easier to finance than one near TBO.
What TBO Means
Manufacturers publish a recommended TBO — for many piston engines around 2,000 hours, with a calendar limit too. It's the point at which the engine should be overhauled to restore it to service limits. For most private (Part 91) operations, TBO is a recommendation rather than a hard requirement, but insurers, lenders, and buyers treat it as a key benchmark. A ‘mid-time’ engine has meaningful hours remaining; a ‘high-time’ or ‘run-out’ engine is at or past TBO.
Why It Drives Value and Financing
Time-to-TBO is one of the biggest factors in an aircraft's value. A mid-time engine finances easily; a near-TBO engine reduces value and may bring a lender reserve requirement or a larger down payment, because the overhaul is a large cost looming. When buying, a run-out engine should be reflected in the price — a cheaper high-time airplane isn't cheaper once you fund the overhaul. Reserve per flight hour toward it. See our engine overhaul financing guide.
Figures in this article are illustrative for the 2026 market and are not offers of credit. Jaken Aviation is a licensed aircraft financing brokerage — a division of Jaken Finance Group — and does not make loan decisions. All financing is subject to lender approval. Tax and legal information is general; consult a qualified professional.
Related Questions
Do I have to overhaul at TBO?
For most private operations, TBO is a recommendation, not a legal requirement — but condition still governs, and insurers, lenders, and buyers treat TBO as a key benchmark. Commercial operations have stricter rules.
How does a high-time engine affect financing?
It reduces the aircraft's value and may bring a lender reserve requirement or larger down payment. Reflect the coming overhaul in the purchase price.
What does an overhaul cost?
A piston single's overhaul is typically a tens-of-thousands-of-dollars event; twins double it; turbines are far more. Reserve per flight hour in advance.
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