As the clock runs down to Monday's sanctions deadline for Russian airlines to hand back more than 400 leased planes worth almost $US10 billion ($A13 billion),foreign lessors are fast losing hope that they will get their aircraft back.
Most of the planes are still flying Russian domestic routes,IBA consultancy says,although Bermuda and Ireland - where most are registered - have suspended airworthiness certificates which usually means they should be grounded.
Aviation was an early business casualty of Moscow's invasion of Ukraine,as the West and Russia imposed tit-for-tat airspace bans. Now,lessors face big writedowns or a long insurance battle as the March 28 deadline looms for terminating plane leases under European Union sanctions.
"I'm afraid that we are going to witness the largest sort of theft of aircraft in the history of commercial civil aviation,"said Volodymyr Bilotkach,an associate professor of air transport management at Singapore Institute of Technology.
Dual registration is not allowed under international rules,but Russia has already moved more than half of the foreign-owned aircraft to its own registry after passing a law permitting this,Russia's government said on Wednesday.
The government also said 78 planes leased to Russian carriers had been seized while abroad and would not fly back to Russia,Interfax news agency said on Tuesday.
Major aircraft lessor Avolon has terminated all its Russian airline leases and repossessed four of the 14 owned aircraft on lease with Russian airlines outside the country,a source familiar with the matter said on Friday.
It wasn't clear if the four planes were part of the 78 reported by Moscow.
Although the planes are insured,the unprecedented nature and scale of the potential losses will likely mean years of litigation between lessors and insurers before any decisions on payouts are taken,analysts say.