A multibillion-pound ‘mega trial’ over hundreds of aircraft stranded in Russia began in the High Court today, one of the most complex and costly cases ever to be heard in the Rolls Building. 

Aercap Ireland Limited, the world’s biggest aircraft lessor, is seeking to recover losses from insurers over jets stranded in the country as lessors took their battle for redress to London.

More than 400 aircraft, worth almost $10 billion (£7.6 bn), have been stuck in Russia since Western countries slapped sanctions on the country over the war in Ukraine - and Russian aircraft lessees did not return the jets.

The case is proceeding in a so-called ‘super court’ - Court 15 of the Rolls Building - before Mr Justice Butcher. 

Insurers are balking at payouts, alleging in part that there has not been a physical loss of the planes yet, that the jets and engines are no longer subject to a lease agreement and that Western sanctions prevent them from providing cover.

Some of England’s most prominent commercial barristers are expected to argue on behalf of the defendant’s that the conflict between Russia and Ukraine could still be resolved, depending on the outcome of the US election. The planes may yet be recovered, they intend to argue. 

Dublin-based AerCap has said it was out of pocket to a ‘colossal’ degree and, along with at least four peers, has lodged a lawsuit that hinges on whether the alleged loss of the aircraft has triggered war-risk insurance policies, which have payout limits, or uncapped all-risk policies.

AerCap, the largest claimant, is suing insurers such as AIG (AIG.N) and Lloyd’s Insurance Company for $3.5 billion (£2.6bn) over the loss of 116 aircraft and 23 engines under its all-risks insurance policy. Alternatively, it is claiming $1.2 bn (£915m) under its war-risks policy, court filings show.

Mark Howard, a lawyer for AerCap, told a preliminary High Court hearing in March last year: 'In the real world, it is inconceivable that we do not recover under one [war risks policy].'

The trial continues.