Valuation in R1 R1

There appears to be a valuation issue in R1. I currently have 183 million in cash and have two terminals as assets. I have a few bonds outstanding. In the rankings page, the valuation is showing negative $1,114,759,988. It looks like other airlines appear to have the same issue. The valuation changed recently. I cannot think of a particular event that may have occurred except perhaps building a terminal. The valuation in the History changed on August 1st 2001 and is related to "building value".