This is different because there is zero market anyone on the planet for current leases at anywhere near prevailing rates right now. We already have terms which include sending them back if we don't pay. Time to make some calls. Not to renegotiate for decades, but for the next couple quarters at least. If they won't accept reasonable terms, stop paying and let them come get them. Not all the planes of course, but what we know we won't need for as long as it would take to get replacements.

Call their bluff. They have zero leverage and won't nuke their own balance sheet over a few month's payment differentials. Offer them interest only for next quarter and interest plus a third of principle (or equivalent) for 2 quarters after that then going back to normal, and if they balk call their bluff and let them eat the full cost with zero income.