Splitting One Purchase Order Between Sea and Air to Cover a Stockout
Sales run ahead of the replenishment cycle, and the answer is rarely all-air or all-sea but a measured split that buys weeks of cover at a controlled cost.
Representative scenario, not a specific client engagement. This page describes how a shipment of this kind is genuinely handled — the constraints, the approach, and where it commonly goes wrong. It does not name or describe a real Transeasy customer. Our two documented project moves are the Mexico container move and the India overweight cargo delivery.
The situation
Sales run ahead of forecast, cover falls below the reorder point, and the replenishment purchase order will not be ready to ship for another two or three weeks. Ocean transit from South China to North European base ports is typically in the region of thirty to forty days port to port, with inland delivery and receiving on top. Done honestly, the arithmetic says the listing goes out of stock weeks before the consignment lands.
The reflex is to air freight the order. On volumetric e-commerce goods that often costs several times the gross margin of the units being rushed, because air is charged on chargeable weight and light bulky cartons pay for the space they occupy. The useful question is therefore not which mode to use, but how much of the order actually has to travel at air speed.
What made it difficult
- Air freight is billed on chargeable weight, so a light bulky carton is charged on its volume at the standard 1:6000 conversion rather than on its scale weight.
- The split still has to arrive in receivable units, which means case packs, labelling and minimum shipment rules apply to each consignment independently.
- Two consignments from one purchase order create two customs entries, two sets of documents, and two duty and import VAT calculations that must reconcile to the original invoice value.
- Lithium batteries, magnets, aerosols or liquids within the range restrict which SKUs can realistically fly and on which service.
How it is approached
The air portion is sized in days of cover, not as a percentage of the order. Take the daily run rate on the affected SKUs, count the days between the projected stockout and the realistic availability date of the ocean consignment, add a margin for receiving, and move that quantity by air. On most ranges this is a small fraction of the order and a very small fraction of the cost of flying all of it.
The mode choice into Europe is not binary. Between ocean and air sit consolidated deferred air services, sea-air routings and China to Europe rail, which typically runs in the region of eighteen to twenty-five days on the main corridors. Where the shortfall is two or three weeks, rail frequently removes the need for air altogether at a fraction of the cost, provided the cargo is acceptable for rail and an origin ramp is reachable.
The split is made at carton level and documented when the booking is placed. The fast tranche takes the highest-velocity lines in whole case packs, each consignment carries its own commercial invoice and packing list describing only what is inside it, and HS codes stay identical across both so the two entries are treated the same way. Retrofitting a split after the export declaration is filed is slow and entirely avoidable.
The decision rule is written down before the emergency rather than during it. Book the ocean or rail leg first so the base volume is secured, then size the expedited tranche against the most recent verified sales rate rather than the forecast that has already been wrong once. The comparison that matters is incremental freight cost against gross margin plus the cost of losing listing rank while out of stock.
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Takeaways
- Air is a quantity decision rather than a mode decision: the gap flies, not the order.
- On the Europe lane, rail often covers a two to three week shortfall at a cost much closer to ocean than to air.
- Chargeable weight, not scale weight, determines what an expedited tranche costs, which makes light bulky SKUs the expensive ones to rush.
- Split the paperwork at the point of booking, because separating an order after the export declaration is filed is far more disruptive than planning it that way.
Frequently asked
Usually yes for a small tranche and rarely for the whole order. Air on volumetric consumer goods can exceed the gross margin of the units moved, so the sensible approach is to fly only the quantity needed to bridge the stockout and send the balance by sea or rail. Size the tranche on the current sales rate rather than on the forecast.
Multiply the daily sales rate by the number of days between the projected stockout and the date the sea consignment is genuinely available to sell, then add a receiving buffer. That quantity flies and everything else sails. Running the calculation per SKU rather than across the whole order usually shrinks the air portion considerably, because only a few lines are actually short.
Yes, and it is routine, but the split has to be declared cleanly. Each consignment needs its own commercial invoice and packing list reflecting only the cartons it contains, with consistent HS codes across both so the two customs entries are treated identically. Arrange the split before the export declaration is filed rather than dividing a consignment afterwards.