I'm sorry, but you are just plain wrong on this.And airlines have not been able to simply walk away from airplane contracts by the dozens, in case you didn't notice. AMR was able to walk away from so much of TWA's fleet because it was TWA's 3rd bankruptcy and it was pretty apparent to everyone that TWA would be liquidated.
WT was thinking about the same thing when I typed my previous statement that I am thinking now: airlines don't dump dozens of modern, marketable aircraft on their first bankruptcy because debtors would rather restructure debt than accept that many aircraft back. By #2 and #3, things change. US is the only airline that has even gotten to #2 and they seem relatively stable for the time being.
Now, within the context of the current industry restructuring environment, would you like to explain how NW or any other airline will succeed at dumping a significant portion of its modern, operating fleet?
First of all, US has terminated a large number of leases in its bankruptcy. Not sure how many exactly, but it was more than 50.
Second, both NW and DL have filed to reject large numbers of leases in their bankruptcies. Over 100 planes for one of them. Now I know that they intend to renegotiate many of these leases and keep the planes, but there is nothing stopping them from rejecting the leases if they choose to do so. So long as there is a business reason for terminating the leases, the judge is going to approve them.
Third, to answer your specific question, it's easy. Just file to reject the leases and get court approval. That's all it takes.