One war, two books: Aggregation crossing from aviation into marine

The direct-market story of the war-risk losses since 2022 is now reasonably well mapped.

On the aviation side, the Commercial Court held in June 2025 that lessors of aircraft stranded in Russia suffered a loss under their contingent war-risk cover as of 10 March 2022, the date of the Russian government resolution the court treated as a restraint or detention.

The Court of Appeal has since granted the war-risk insurers permission to appeal on all grounds, with the hearing expected early next year; contribution claims against the reinsurers of the Russian operators’ policies were dismissed in May; and the operator-policy trial, governed by Russian law, opened on 5 October.

On the marine side, the same period produced the vessels trapped in Ukrainian ports from February 2022 — with the detention provisions of war-risk wordings converting prolonged deprivation into constructive total losses — and then, from late 2023, the Houthi campaign in the Red Sea, whose casualties have already reached the courts.

Each of these has been told mostly as a coverage story. The reinsurance story, which is an aggregation story, is only beginning.

Before the question of how many events comes the question of which book.

The Rubymar dispute, in which hull underwriters rely on the war, strikes and malicious-acts exclusions of an Institute Time Clauses policy against an owner claiming a total loss, is at bottom a contest over the boundary between marine and war cover.

Wherever that boundary falls on particular facts, it decides which treaty the loss enters, and therefore which aggregation language will count it.

A whole-account marine treaty and a war or political-violence excess-of-loss contract may answer the event question very differently for the same casualty, and a cedant writing both may find the answer turns on a coverage finding made in a proceeding to which no reinsurer was a party.

Aggregation is where the two books converge.

The treaty and retrocession architecture protecting aviation and marine war accounts — event-based excess of loss, whole-account covers, war and political-violence sections — is built on the machinery of the occurrence: the event, the originating cause, the hours clause, and the unities of time, place, cause and intent that tribunals have applied since the Dawson’s Field award.

That machinery was refined on hurricanes, earthquakes and, after 2001, terrorism, and was most recently stretched by the pandemic, when the Court of Appeal in Unipolsai v Covéa upheld an award treating Covid-19 as a catastrophe for the purposes of an hours clause.

It was not built for a slow-motion, state-directed appropriation unfolding across an entire jurisdiction, nor for a months-long campaign of discrete missile and drone attacks along a shipping corridor.

The market does hold aviation war precedent from the last time a state seized an airline fleet, and it is instructive precisely because it points both ways. After Iraq’s invasion of Kuwait in 1990, the requisition of fifteen Kuwait Airways aircraft at Kuwait airport was held to be a single occurrence under the airline’s own policy, confining recovery to one limit. Yet in Scott

v Copenhagen Re the Court of Appeal held that a British Airways aircraft stranded at the same airport by the same invasion, and destroyed months later in coalition bombing, did not arise from the same event as the Kuwait Airways losses for the purposes of a reinsurance aggregation clause.

Same war, same airport — one set of losses aggregated and the other did not, because the test looks to the unity of each loss’s circumstances, not to a shared geopolitical origin.

Now set the recent facts against that machinery.

The Russian aircraft loss involves hundreds of aircraft, leased to many airlines and held at dozens of airfields, and a judgment fixing a single loss date for the lessors’ claims. Is that one event for reinsurance purposes, many losses with a common originating cause, or something the wording does not contemplate at all?

The aggregate limits at the direct level already shaped recoveries in the lessor-policy claims, and how a shared aggregate is divided among multiple claimants has not yet been tested.

The trapped Black Sea tonnage raises the mirror image: each vessel’s detention ripened into loss individually, on its own clock, under its own policy — yet every one of them traces to a single day’s invasion.

And the Red Sea presents the terrorism-adjacent pattern in a new key: separate attacks, separate vessels, separate weeks, one campaign, one belligerent.

Whether an hours clause, an each-and-every-loss structure or an originating-cause aggregator counts that as one, several or dozens will move very large sums between cedants, reinsurers and retrocessionaires.

Two features make the next phase distinctive. First, the direct-market judgments will not answer the reinsurance question, but they will furnish its raw material. Findings about when and how the loss occurred — the loss date, the characterisation of the Russian measures as restraint or detention, and whatever the Court of Appeal and the operator-policy trial add — become the factual substrate on which aggregation disputes are argued, even though treaty wordings deploy different concepts for different purposes.

The gap between what a court found for coverage purposes and what a treaty means by event is precisely where these disputes will live. Secondly, much of this will be resolved out of public sight. Reinsurance disputes default to arbitration, and the market may never see a reasoned, citable body of aggregation decisions on these facts. That places unusual weight on the quality of each tribunal’s reasoning, and on the parties’ choice of arbitrators fluent in both the aviation and the marine idiom.

None of this requires a view on how any particular dispute should come out, and I do not offer one. The observation is structural: the same rupture has entered the market through two classes of business, and it will leave through aggregation language written for other perils.

Cedants approaching the 1 January renewals, and reinsurers pricing them, are in effect drafting the next decade’s case law now. The event definition is worth reading this season with the last four years in mind — because the perils these clauses will be tested against are no longer hypothetical, and the cost of an ambiguous aggregator is no longer abstract.

Russell D. Pulver, MCIArb, is an independent international arbitrator and mediator (International Alternative Dispute Resolution, www.international-adr.com), a member of the ARIAS (UK) arbitrators panel, and a retired US federal administrative law judge. The views expressed are the author’s alone and address matters of law and process, not the merits of any pending dispute.