The AA number is either an error or the writers are trying to sensationalize the story. If my memory is correct AA had $1.3 billion in cash on hand per their 10Q of 6/30/2001.
(1) the cash number is an error, or (2) they are excluding marketable (liquid as in money markets) securities to make more of a point.
Anyway, even with near zero cash the airlines might be able to borrow money to see them through rough times.
The airline is similar to your personal life. My checking account had $805 the other day. I'm not going bankrupt this week. I could draw down funds in savings accounts or I could borrow money before my next deposit of income into my checking account.