At the time of the sale to Owner 2, Owner 1 is throwing away $50,000 by selling half the $200,000 plane for $50,000. He only realises that "loss" when owner 2 sells.
If he is upset by the concept of owner 2 gaining $50,000 at the later date, then he shouldn't give it to him in the first place.
The equity concept may work - where Owner 2 puts in $50,000 to buy a stake in the aeroplane with the requirement to pay 1/2 of all the fixed costs. If Owner 2 wants to get out, then the plane share is sold and from the proceeds Owner 2 is paid his $50,000 indexed at CPI (or RBA cash rate, or any other mutually agreeable index) and Owner 1 gets the rest. That way owner 1 retains all the bonus equity for the good deal in buying the plane.