If you liquidate a subsidiary of a holding, and the subsidiary is solvent, I understand from the Wiki that any aircraft owned by the subsidiary are sold at 15% of book value. Hmm, sounds a little harsh. So that means that if possible, you should asset transfer the aircraft back to the holding before liquidation - but that's only possible if the aircraft are debt-free. So I'm thinking, what other ways could you extricate the asset value of the aircraft if you wanted to liquidate?
Sell them on the market. The 15% rule is follwing the market - if you can't sell it for more you would get a buy order by the public aircraft trader - so prior liquidation you can try to sell it by yourself.