Though airlines have been through their own financial crisis with bankruptcies rampant throughout the industry, the financial bailout is as important to them as any of their direct bankruptcy dealings. Without the financial industry, the airlines lose one of the most important sources of business travelers and they may lose their lucrative credit card contracts and access to millions of dollars of emergency cash.

Last week’s bailout of Citibank buoyed airline stocks by the tune of about 10 percent. MarketWatch pointed to the importance of the financial sector’s use of business class. The simplistic approach seemed to indicate that with Citibank being bailed out, the good times of business class and first class spending would continue unabated. I don’t think so.

A look in another financial corner reveals the airlines’ agreements with credit card companies. Citibank is one of the largest issuers of airline affinity cards. With the finance companies having liquidity problems, the credit difficulties will eventually land in the laps of airlines that have made major deals with these troubled banks.

Just last week United airlines reached an agreement with its largest credit card payment processor, reportedly JPMorgan Chase & Co., suspending UA’s obligation to post or maintain additional cash reserves above the current $25 million if its balance of unrestricted cash, cash equivalents and short-term investments dips below $2.5 billion. In return, UA granted JPMorgan an $800 million security interest in owned aircraft.

As anyone examining the balance sheets of the airlines knows, these financial instruments and the linkage between credit card processing and maintenance of cash and credit flow are a complicated dance. In the old days, the banks with supposedly solid balance sheets, in effect, propped up the airlines. Today banks and credit card issuers cannot be so generous or patient with returns.

As the credit crisis continues, look to see the airlines being drawn into the bailout mix more and more as their contracts with banks and creditors begin to unravel should the largest banking institutions continue to flounder.