There is another strong reason why B tries to coax the FAA to lift the grounding before the end of the year. Looking at their public 3rd quarter financial statement, they obviously booked all the undelivered aircraft fully as inventories. Now the financial year is closing soon and they have to produce a full report on the business year 2019. I doubt that any public company is allowed to add nearly 400 undelivered aircraft at the full sales price to their inventories when they are not airworthy at the time of the statement. That would probably provoke more then just a letter from the SEC. And the effect on the balance sheet of even a small value deduction on those aircraft not complying with regulations would be abysmal.