mmmm, that too. Nonetheless, leasebacks are not an unreasonable way to free up cash for other uses. One can also sell bonds backed up by the equipment which is the other thing commonly done (take a look at AAs debt to asset ratio below). You still have title but unless you can pay the bond premiums the bond owners can wind up with them. Airlines are very capital intensive organizations.

https://www.macroaxis.com/invest/bond/
AAL

Not saying NK is making a lot of money right now, just saying leasebacks for airliners are not at all uncommon.