You are correct that American did acquire TWA for $500M cash but American also had to assume all the debt on the leased TWA planes and keep making those operating lease payments. It wasn't just $500M cash and keep everything else. Also the creditor committee agreed with the 363 sale. It wasn't just imposed on them by the court.

How many planes does Spirit own that aren't leased or encumbered that could be acquired?

Do you really think any BK court will just hand over the assets that are encumbered when those entities that own the planes are saying they want their assets back? Spirit isn't the owner of them. They just lease the planes. I don't recall in any BK ever any owner of an asset losing it because some entity that was leasing it filed BK. They either go back to the owner, or they are transferred with concurrence of the owner. Especially when they are in default of the lease agreement as Aercap claims.

You keep chirping "363 asset sale" and "TWA" but you leave out the key points that the creditors and lessors agreed and the ongoing payment of lease debt had to be paid by American as well.