Insurers have lost a London High Court case for the right to appeal a billion-dollar decision over jets trapped in Russia since the Ukraine invasion.

The case, related to what was believed to be the largest aviation insurance loss ever, was said to involve 147 aircraft and 16 stand-alone engines, valued at more than $4.5 billion, leased to 18 Russian airlines, Reuters has reported.

It is part of a wider loss involving more than 400 aircraft with a value in excess of $10 billion that Russia seized after the onset of hostilities.

Lessors and operators were at loggerheads with their insurers over claims for compensation and the courts ruled against insurers.

The court had ruled they had to pay more than a billion dollars from their war risk policies to cover the loss of the jets.

This week, a High Court judge refused permission for the insurers to appeal that decision and put off the questions of costs for another day.

Reuters said court filings showed that lawyers for Irish-based AerCap, the world's largest lessor and the biggest claimant in London, said its legal expenses alone ran to around 81 million pounds (about $111 million).

AerCap was joined by Dubai Aerospace Enterprise, Merx Aviation, KDAC Aviation Finance, Falcon and Genesis in claims against a string of insurers, including AIG, Lloyd's, Chubb, Swiss Re and HDI Global Specialty.

The lawsuit had focused on almost 150 jets and some engines, valued at up to $4.7 billion. But settlements, including on the first day of the trial last October, whittled the numbers down.

KDAC settled all its claims during the trial, while AerCap struck a deal with Swiss Re and HDI. DAE settled with all war risks insurers and Merx settled with all war risks insurers apart from Fidelis, Reuters said court filings showed.