How abrasive the work has to be is decided before we arrive
That is the whole technical argument, and it settles the question before cost is raised at all. Standard airframe cleaning doctrine already splits the work in two. A dry wash lifts airport film, dust and light soil where water is undesirable or impractical, and it is expressly not suitable for heavy carbon, grease or oil, particularly around engine exhaust. A wet wash removes oil, grease, carbon and most soils, and removes neither corrosion nor oxide films. Once contamination has sat and bonded, the light method is off the table and the work turns mechanical. Modern basecoat and clearcoat systems build roughly 2.0 to 2.5 mils of clearcoat. Every correction pass spends some of that permanently, and the only way to put it back is a strip and repaint, typically five to seven weeks on the ground. A program keeps the aircraft inside the range where the non-abrasive method still works.
The corrosion argument, for the director of maintenance rather than the principal
Washing removes acidic airborne contaminants from the surface, and filiform corrosion under paint is inhibited by keeping the aircraft below 70% relative humidity and by washing those contaminants off. Belly soils are worse than they look: accumulated hydraulic fluid, fuel, exhaust soot and grease trap corrosive material against structure and worsen the attack on it. FAA AC 43-4B puts corrosion inspection frequency and treatment on the operator, informed by the manufacturer's recommendations or the operator's own program. A recurring appearance visit is, in practice, a recurring close-range look at the skin, the seals, the gear bays and the belly by people who see the same aircraft repeatedly and notice what has changed since last time. On-demand gives you that look once or twice a year, if the scope reaches that far.
What touches the aircraft stays the same every visit
A program is also a commitment about chemistry. Exterior cleaners qualified to AMS 1526 are specified not to corrode aluminium, magnesium or steel alloys and not to harm acrylic glazing or painted and unpainted surfaces. Boeing's D6-17487 qualification for exterior cleaners, waxes and polishes runs a harder battery still: sandwich corrosion over seven days with product-saturated filter paper between faying aluminium surfaces under cyclic humidity and heat, acrylic crazing, immersion corrosion, paint softening, and hydrogen embrittlement to ASTM F519, four notched cadmium-plated specimens immersed for 150 hours at 45% of load. A consumer product cannot have passed a test it was never submitted to. On a program the same qualified products meet the same airframe every few weeks, which is a different proposition from whatever is to hand the night before a trip.
The cabin is written around recurrence already
Gulfstream's own completion center maintenance handbook, chapter 12-26-00, treats the cabin as eleven separate material problems, with a different procedure for wood, granite, Lexan, vinyl laminate, plating, stainless steel, leather, vinyl, Aermat rubber, carpet and fabric. It builds a schedule into the procedure itself: the urethane wood finish is non-absorbent, so it must be cleaned before every third polish application or the polish builds up, and silicone-based polishes leave an oily residue that can prevent a later repair. Operator guidance is blunter still. Aggressive cleaning of seat covering materials and carpet can remove the fire retardant, and no amount of cleaning harder next time puts that back. Frequent gentle work stays inside those limits. Infrequent work invites the aggressive pass that breaks them.
On-demand has a failure mode, and it is predictable
It becomes crisis-demand. The call comes the evening before a trip, the aircraft needs three days of work, and there is one night available. That is the least controllable way to buy appearance work and the least likely to produce a result you would show anyone. Scope gets set by the clock instead of by the aircraft: correction that wants daylight and two days gets an hour under hangar lights, and a cabin that wants material-by-material attention gets a wipe-down. We take those calls, seven days a week with AOG dispatch around the clock, and we will tell you plainly that the same work done unhurried comes out better every time.
What changes the answer
Utilisation first. Below a few flights a month a fixed interval starts buying work the aircraft has not earned, and we will say so rather than sell it. Then where it sits: a hangared aircraft in dry air is a different problem from one on the ramp collecting rain, pollen and exhaust film. Then the age of the paint. Manufacturers recommend strip and repaint every five to six years, industry practice runs nearer seven, and on a finish already approaching that there is no sense spending clearcoat on correction, so the program shifts towards protection, belly cleaning and cabin work. And a sale inside a few months changes it completely. At that point one properly scoped pre-sale detail does more than a program started too late to show any history.
Where the program costs more, and why that is the right call
A program is not the economical route and we do not present it as one. It is a standing commitment, and across a year it usually means more visits than calling us when the aircraft looks tired, not fewer. What you are buying is a standard that never drops. A recovery detail and a maintained standard are two different products: one returns a drifted aircraft to presentable, the other means it never drifts, and buying the first repeatedly does not get you the second. A full interior and exterior on a midsize jet, done to a professional standard, is a five-figure job before condition or deadline are counted. The point of the program is that the aircraft is never in the state where a reset of that depth, or correction, is the only way out.