Block space agreements, allotments and charters — what is the difference?
A block space agreement commits you to buying a set amount of air cargo capacity on specific flights, whether you use it or not. Here is how BSAs differ from allotments and charters, and when each is worth signing.
A block space agreement is a fixed commitment to buy a set amount of cargo capacity on specific flights or lanes, usually monthly or annually, and you normally pay for that space whether you fill it or not. An allotment reserves capacity at a fixed price under a longer-term contract. A charter is the whole aircraft.
What exactly is a block space agreement?
A block space agreement — almost always shortened to BSA — is a contract between a freight forwarder or consolidator and an airline. You commit to taking a defined quantity of cargo space on a named lane or set of flights, over a defined period.
The defining feature is the commitment. BSAs typically carry a guaranteed cargo commitment, which means you are charged for the space whether or not you fill it. That is the trade: the airline gets predictable revenue, and you get predictable capacity and a better rate than you would buy on the spot market.
BSAs sit between two extremes. They give you more certainty than buying spot, and less exposure than chartering an entire aircraft.
How is an allotment different from a BSA?
The two overlap enough that the terms are often used interchangeably, which causes real confusion in contract discussions.
An allotment is reserved capacity held for you under a longer-term contract at a fixed price. The emphasis is on the reservation and the price certainty.
A BSA emphasises the commitment. It is a fixed space commitment for a specific lane or flight over a stated period, and it usually comes with the obligation to pay regardless of use.
In practice, whether a given contract behaves like an allotment or a BSA depends less on what it is called than on two questions: is the price fixed for the term, and are you liable for unused space? Ask both before signing, whichever word appears on the document.
When does a charter make more sense than a BSA?
A charter is the whole aircraft. You are not buying a portion of the hold alongside other shippers; you are buying the flight.
Charters make sense when the volume genuinely fills an aircraft, when the cargo cannot be consolidated with other freight, or when timing is so critical that scheduled capacity is not reliable enough. Project cargo, outsized shipments and emergency lanes are the usual cases.
The distinction that matters commercially: a BSA is explicitly short of chartering an entire aircraft. If you find yourself topping up a BSA with regular ad-hoc charters on the same lane, the BSA is probably sized wrong.
What does a BSA actually cost you when it goes wrong?
The risk in a BSA is not the rate. It is utilisation.
If you commit to space you do not fill, you pay for it anyway, and that unused capacity comes straight out of margin on the shipments you did move. A lane that looks profitable at 90% utilisation can be loss-making at 60% without anything visible changing in your rate card.
This is why BSA holders tend to watch utilisation more closely than they watch price. The question is rarely "did we get a good rate" and almost always "are we filling what we committed to, and if not, what are we doing about it this week rather than at month end".
How do forwarders decide how much space to commit to?
Most start from historical volume on the lane and commit below their average rather than at it, because the downside of under-committing (buying spot to top up) is smaller and more predictable than the downside of over-committing (paying for empty space).
The harder part is what happens after signing. Utilisation has to be tracked against the commitment continuously, and unsold space has to be actively pushed — to co-loaders, to partner agents, or through more aggressive pricing on that lane — while there is still time to fill it.
That is an operational discipline problem more than a procurement one, and it is where most of the money is won or lost on a BSA.
Common questions
Do you have to pay for unused block space?
Usually yes. Block space agreements typically include a guaranteed cargo commitment, with the buyer liable for the capacity whether or not it is used. Confirm this explicitly — it is the single most important commercial term in the contract.
Is a BSA the same as an allotment?
Not quite, though the terms are often used loosely. An allotment emphasises reserved capacity at a fixed price under a long-term contract; a BSA emphasises a fixed volume commitment on specific flights or lanes. Ask whether the price is fixed and whether you are liable for unused space, rather than relying on the label.
Can a freight forwarder hold a BSA and still buy spot capacity?
Yes, and most do. A BSA covers baseline volume on a lane; spot capacity handles peaks and anything the committed space cannot absorb.
Who typically holds block space agreements?
Consolidators, NVOCCs and trade-lane specialists with consistent volume on defined routes — the businesses whose lane volume is predictable enough to commit against.
Stop losing quotes to whoever answered first.
Bring a real RFQ from last week. We will run it end to end and you can judge the output yourself.