Wiping out the investors does profound downstream harm because it means that future investors will be less likely to invest in these kinds of companies, or smaller companies striving to occupy similar roles.
Moreover, union obligations cannot always be petitioned in bankruptcy proceedings. This has resulted in company assets being dissolved altogether, instead of sold off and used, in some cases in the past.
To be clear, there won't be a "wipe out" at least in the "floor fell out from left field" sense.
If a bankruptcy becomes likely, investors will start selling Boeing stock to recover what they can. Creditors will start calling Boeing bonds, if applicable. Remember, "the market has priced it in" is a meme for a reason.
So far we haven't seen anything like that yet, just otherwise normal reductions in stock valuation following lackluster business performance.
However, Boeing is courting the possibility of having their credit ratings reduced to junk bond status by Moody's[1] and S&P[2] and that would certainly be a potential sign of the end times coming. Getting slapped with junk bond status literally means lenders should not consider Boeing reasonably solvent.
Moreover, union obligations cannot always be petitioned in bankruptcy proceedings. This has resulted in company assets being dissolved altogether, instead of sold off and used, in some cases in the past.