I have a suggestion regarding leasing. Right now I have 6 planes 'parked' since I'm trying to correct my quick over expansion in the start of the game. They are planes I don't want to return to service however I have long term leases on them. (Yes poor planning on my part). I have two options, park them and absorb the loss on the lease each week or pay up front fee to return them. So a possible suggestion for future games.
1)Allow them to go to storage (this has been suggested in the past)
The savings you are saving if you store them is to dodge the high parking fee if you have too many idling. storage is actually quite expensive compare to sitting them on ground without going thru maintience. Plus you are paying the lease when you storing it, so no real savings here.
2) When you initially lease the plane you are given an option to pay an additional fee based on the plane size to allow you to sub-lease the plane out. The fee would be such that you could make some money off the deal but nothing crazy. This way it allows planes not to sit idle and gives other players who might be looking for those planes a chance to get there hands on some.
never in real world you are allow to get income from leasing out a lease object. and it is way too easy to abuse due to inflation in the game.
If you are having a long lease and won't put them back in service just terminate it. faster you terminate more money you save in long term.