We'd need a bit more information about this letter in order to help you: who it's from, where the shares are held, what exactly was said, and what you're seeking.
Computershare is the transfer agent for UAL stock. They are ultimately who would have all records of stock ownership. I would contact them first. Their number is: (800) 919-7931
Brian Pinkston, CFA, CFP® Financial Advisor Anchorage, AK
Here is a link to Computershare, http://www.computershare.com/us/Pages/default.aspx the transfer agent which Brian referenced. The transfer agent is the firm that keeps the records of who owns the stock of a company. There are a few different firms that do this for most major U.S. companies and as Brian mentioned, this is who UAL uses.