Freight

Which SKUs to fly, which to leave on the boat

A late boat does not make every product worth bridging by air. It makes a handful of them worth it, and finding those few is a five-minute screen, not a full recalculation of the catalog.

Marcus VolstedCo-founder, Restocio Published 18 September 202610 min read

Only the SKUs where the stockout would cost more than the air premium are worth bridging by air, a small slice of a catalog. Rank by what is at risk in the gap, then run the bridge arithmetic on the ones near the top. Everything else is cheaper left on the boat, even while it runs a little light for a few weeks.

This is not a new formula. ABC analysis already argues that a catalog should be ranked by revenue at risk rather than by last year's sales, and the air versus sea bridge calculation already works out, for one product, how many units to fly and whether the premium pays for itself. Neither post asks the question this one does. Across a whole catalog, which products actually clear that bar, and which are cheap enough to let run out for a few weeks instead.

Two rankings, and they measure different things

Revenue at risk answers how much money is riding on a product right now. It is the quantity currently due, multiplied by what those units sell for, and it is what makes a live ranking useful instead of a spreadsheet nobody reruns. A product with plenty of cover scores close to zero no matter how big it usually is, and a product about to go dark scores its full replacement value. That is the size and urgency half of this decision, and ABC analysis for inventory is the fuller argument for why last year's sales are the wrong axis for it.

The bridge calculation answers a different question entirely: does flying this specific product's shortfall pay for itself. Multiply the days you would be out of stock by your daily sales to get the units that need to fly, then divide the extra freight those units cost by the margin you earn per selling day. A short payback means the premium buys itself back fast. A long one means you are paying air rates to protect not very much. The full working is in air or sea freight, and how to work out the split.

A product can score high on the first and fail the second. A heavy, thin-margin bestseller can carry a large revenue-at-risk number and still lose money in the air, because the freight premium scales with weight and the payback scales with margin, and neither cares how many units the product usually moves. A product can also do the reverse: modest revenue at risk, light, decent margin, and a payback measured in days. Ranking on either number alone misses one of the two failure modes.

The screen before the arithmetic

Running the full bridge calculation, weight, freight rate, margin and daily sales, on every product in a catalog every time a shipment slips is not realistic when the decision has to be made in days. Plenty of stores also do not have current weight and margin typed in for every SKU, which is its own limitation and worth fixing before any of this is worth doing at all.

Check revenue at risk first. Only run the bridge math on what is left. Anything with real money on the line and a light, decent margin is worth the full calculation. Most of what is left is cheaper to leave on the boat.

Pull the revenue-at-risk list first, since it is already sorted and already live if a store runs the ranking abc-analysis describes. Anything sitting near the bottom of it, with little or nothing due, is not worth a second look regardless of how the bridge math would come out, because there is nothing much to protect. Only for the products carrying real money is it worth pulling out the weight and the margin and running the actual payback.

A second, cheaper filter sits inside that shortlist. Divide margin by weight, or price by weight if margin is not to hand, before running the full formula. A product that is heavy for what it is worth rarely survives the bridge calculation, because air freight is charged on chargeable weight, the greater of volume or mass, and a low-value-per-kilo product pays that premium on every unit it flies. Treat this as a rough sort, not a verdict. It is worth checking before the full arithmetic, not instead of it, since the shortcut can be wrong at the margin.

A worked catalog

Say a sea shipment is running about a month behind, and four different products on it are sitting at different points on the shelf, so each has a different number of days actually uncovered by the time the boat lands. Using the same $6.50/kg air and $0.90/kg sea rates as the worked example in air or sea freight, so the two examples line up.

Product	Daily sales	Days uncovered	Units to fly	Freight premium	Money exposed in the gap	Payback	Call
Phone stand, light, decent margin	14	25	350	$294	$7,000	2.3 days	Fly
Cast iron trivet, heavy, thin margin	3	30	90	$554	$2,160	30.8 days	Leave it on the boat
Ceramic mug, bestseller, mid-weight	40	27	1,080	$2,722	$17,280	13.6 days	Borderline, worth the full check
Niche accessory, light, thin margin	2	15	30	$34	$360	8.4 days	Pays back, rarely worth the hassle

“Money exposed in the gap” here is daily sales times days uncovered times sell price, a narrower number than a live revenue-at-risk ranking, which prices the whole recommended order rather than just the days that would go unmet. It is worked out this way only to make the four products comparable on the page.

The phone stand is the easy case: real money on the line and a payback under three days. The trivet fails on both counts, so leaving it on the boat is not a close call. The mug is the interesting one. It carries the biggest number in the whole table by a wide margin, and the payback still runs into the second week, because its weight eats a real share of the premium. Most merchants would still fly it, but that is a judgment call, not the obvious yes the phone stand is. The niche accessory pays back fast in ratio terms and is still probably not worth the trouble, since splitting a shipment and receiving it in two dated batches, a real cost air or sea freight's own FAQ names directly, adds friction too, and $360 rarely justifies it.

The decision in one table

The four products above sit in four different cells of the same simple grid: how much is actually at stake in the gap, against how fast the premium pays for itself.

	Bridge pays back quickly	Bridge pays back slowly
Real money at risk	Fly. Not a close call.	Worth the full check. The stockout may still be expensive enough to justify it, and here the arithmetic is doing real work rather than confirming what was already obvious.
Little at risk	Technically profitable, rarely worth the operational cost of splitting the order.	Leave it on the boat. Not a close call either.

Both "real money" and "quickly" are judgment calls, not fixed numbers. A store with thin cash reserves might treat two weeks as slow. One that flies routinely might not. The worked example in air or sea freight came out at a 7.2 day payback and called that an easy yes. Set your own line and apply it consistently rather than deciding case by case in the moment, which is exactly when a bestseller gets flown out of habit instead of arithmetic.

What Restocio already does, and what it leaves to you

Restocio already runs the size half of this continuously. The revenue-at-risk ranking sits live on every store, sorted by exactly the number this triage starts from, so there is no spreadsheet to rebuild before checking it. What it does not do is judge the second half for you. If a faster mode is switched on and the sea order alone would land late, the recommendation adds a bridge quantity on that mode for whatever product needs one, sized by days and daily sales the same way the calculation above works, not by whether the extra freight is worth paying. That is deliberate. The same rule that keeps margin from moving or hiding a row anywhere else in the app keeps it out of this calculation too, so two products selling at the same daily rate get the same automatic bridge quantity once air is switched on, whether one is a heavy, thin-margin item and the other a light bestseller. Sell faster and the bridge grows, exactly as it should. Sell for more and it does not move at all. Deciding whether to actually act on that recommended bridge, product by product, is the judgment this page is about, and it stays yours to make.

When the honest answer is wait

Most of a catalog, most of the time, is the boring case. A product sitting on plenty of cover against its usual transit time does not need any of this, since nothing is uncovered yet. Among what is genuinely short, the honest answer for a good share of it is still to wait: modest money on the line, thin margins, or a weight that lets the air premium eat whatever it would earn back. Letting a slow, low-margin product run empty for two or three weeks is not a planning failure. It is the correct call, arrived at on purpose instead of by default, which is the actual difference between this exercise and never checking at all.

One limitation is worth stating plainly. This whole triage runs on your weight and margin data being current. A cost price nobody has touched since the product was created, or a weight field still sitting on Shopify's default, will feed the payback formula a wrong input and hand back a confident wrong answer, the same trap air-vs-sea-freight names for a single product. Fix those two fields on the shortlist before trusting the number, not after.

Common questions

How do I decide which SKUs are worth flying when a shipment is late?

Two checks, in that order. First, pull the revenue-at-risk ranking, the one abc-analysis describes, and set aside anything near the bottom of it, since there is little money on the line whatever the freight math says. Second, for what is left, run the bridge calculation from air or sea freight: units to fly times the extra cost per kilo, divided by the margin you earn per selling day. A payback of a few days is an easy fly. One measured in weeks is usually cheaper to leave on the boat.

Is my best-selling product automatically worth flying?

No. Revenue at risk and bridge economics are different axes, and a bestseller can fail the second one while it tops the first. A heavy product with a thin margin pays the air premium on every kilo and earns it back slowly, so a big, popular, low-margin item can be a worse candidate than a smaller product that happens to be light and profitable. Check the weight and the margin before assuming size decides it.

What is revenue at risk, and how is it different from the air freight bridge calculation?

Revenue at risk is the quantity currently due on a product multiplied by what those units sell for, and it tells you how much money is riding on getting that product right, argued in full in ABC analysis for inventory. The bridge calculation is a separate question about one product: how many units need to fly to cover the gap until the boat lands, and whether the extra freight for those units pays for itself. The first tells you where to look. The second tells you whether to act.

Does Restocio decide which SKUs to fly for me?

It ranks every product by revenue at risk live, and if a faster mode is switched on, it adds a bridge quantity to the recommendation for any product whose sea order would land late, sized by days and sales rate. It does not check whether the extra freight is worth paying for that specific product, because margin has no say in what the app recommends, on purpose, the same rule that keeps it from moving or hiding anything else in the app. Deciding whether to act on a recommended bridge is still a call the merchant makes.

What if several SKUs pass the test but I cannot afford to fly all of them?

Rank the ones that pass by how fast the bridge pays back, not by size, and fly the fastest paybacks first. A product with a two-day payback is a safer use of limited air budget or capacity than one with a three-week payback, even if the slower one carries a bigger total number. Whatever does not make the cut this time either waits for the boat or gets a partial rail bridge if that mode is switched on and fast enough to help.

Marcus Volsted

Co-founder, Restocio

Marcus co-founded Restocio and works on it daily with a Swedish importer who plans their purchasing in it every working day. Restocio is built in Sweden by two founders, one Swedish and one Danish, and Marcus is the Danish one. Why we are building it.