Two identical aircraft, two identical borrowers, wildly different payments. The variable is the lessor — and almost nobody asks about it.

An owner evaluating an operating lease against a loan will typically approach it as a question about themselves. What is my tax position? How long do I intend to hold? What does my balance sheet look like? Do I want the depreciation?

All reasonable questions. None of them explains why two lessors will quote the same aircraft, for the same operator, with monthly payments that differ by a meaningful margin.

That variance is not about the operator at all. It is about what each lessor believes the aircraft will be worth at the end of the term — and, more precisely, about whether they have any independent basis for the belief.

The mechanics are simple enough. In a residual-based structure, the lessor sets a terminal value at the outset and the periodic payment is priced against the difference between acquisition cost and that residual. A higher residual means the operator is paying for less of the aircraft over the term, which means a lower payment. A lower residual means the reverse.

So the residual assumption is the single largest driver of the economics. And a residual assumption is an act of judgment about a specific airframe: its maintenance status, its total time, its engine program position, its place in the model’s lifecycle, how that type has actually behaved in the secondary market, and what the market for it is likely to look like in five or seven years.

Making that judgment requires knowing the asset. A lessor who does not know the asset has one option available, which is to assume conservatively and let the operator absorb the difference. That is not a credit decision. It is a capability limitation being passed through as a price.

This matters far more in 2026 than it did five years ago, for a structural reason. Roughly three-quarters of for-sale business aircraft inventory is now sixteen years or older — up from 57 percent in 2015. The available market has aged substantially, and older airframes are precisely where residual judgment gets difficult and where published guidance stops being sufficient.

A five-year-old midsize jet, program-enrolled, with modest total time, presents a manageable problem. There are comparables, a clean maintenance picture, and a residual that can be drawn from guidance without much independent thought.

An eighteen-year-old large cabin aircraft with substantial hours, no engine program enrollment, a heavy inspection approaching, ownership through a trust, and a Part 135 management agreement layered on top presents a different problem entirely. What is it worth after the inspection? How much does the absence of an engine program actually reduce value — as opposed to how much does a cautious desk assume it does? Does the charter utilization degrade the asset or does the professional maintenance oversight that comes with a certificated operation improve its records and condition relative to a comparable Part 91 airframe?

Those questions have real answers. They are just not in a guide, and a desk that sees this profile twice a year is not going to develop one.

The practical consequence is that a great many owners have been quietly steered away from the aircraft they actually wanted. The search gets restricted to newer, lower-time, program-enrolled airframes — not because the mission requires it, but because those are the aircraft the lender treats favorably. Which means the search has been restricted to roughly the last quarter of available inventory, during a period when that quarter has been the scarcest and most expensive part of the market.

One operator running a mixed fleet described it with some resignation: the aircraft they wanted were consistently the ones their lender liked least, and the aircraft their lender was comfortable with were consistently already under contract to someone else.

None of this means an operating lease is the right answer. Frequently it is not. An owner intending to hold through the airframe’s remaining economic life, who values the depreciation benefits available under current law and wants the residual upside, is often better served owning the aircraft outright. An operator upgrading every four to six years, or one who would genuinely rather transfer residual exposure to a party better equipped to carry it, is often better served by a lease.

That decision should turn on hold period, utilization, tax position, and appetite for residual risk. What it should not turn on is a lessor’s inability to underwrite the terminal value — which is what quietly drives it more often than anyone admits, because the limitation never announces itself. It just shows up as a payment.

The question worth asking early, before the term sheets arrive, is not what rate is available. It is: what residual are you assigning to this specific airframe, and what is that based on? The answers vary enormously between capital sources — considerably more than rates do. That variance is where the economics of the transaction actually live.