I have also received a claims form. AFAIK I could only have received the form for 2 reasons:

1. I complained to UAL that they sent me a USD 50 domestic US check, impossible to cash outside the US, to my address in Sweden as compensation in a lost luggage matter (After sending I was able to cash it in before the bankruptcy filing).

2. The balance on my Mileage Plus account.

Looking at the claim form I can see no reason why I can't send it in to protect the value of my Mileage Plus balance, valuing my mileage balance at the "standard" (and slightly inflated) value of USD 0.02 per mile.

Without being an expert on US banruptcy law, I guess that I can even claim that my miles deposited with Mileage Plus is an unsecured priority claim of "up to USD 2,100 of deposits toward purchase, lease or rental of property or services for personal, family, or household use - 11 U.S.C. § 507(a)(6)" as stated on the claims form.

The questions are only is it worth the trouble and do I have anything to lose?