Toward the end, Alvin Lindbergh Feldman, a rising star for 10 years in the airline industry, must have felt under siege.

In the last few hours of his life, it must have become apparent that he was losing his six-month fight to keep Continental Airlines from being taken over by Texas International Airlines.

Hours before the 53-year-old Continental chairman apparently shot himself to death in his executive office, he was helping prepare a news release announcing that a consortium of banks would withdraw its support from a proposed employe stock ownership plan that would have thwarted the takeover.

But even before the banks pulled out, Continental's plan had run into other, possibly fatal, setbacks. Last week, a Senate-approved tax provision that would have smoothed the way for the employe-ownership plan was killed in a House-Senate conference committee. Then, the Civil Aeronautics Board gave Texas International tentative approval to acquire Continental. In Nevada, a federal judge said he would rule against a motion Continental had sought that ultimately would block the takeover.

And, Feldman was facing a board of directors meeting scheduled today.

This is the stuff of business, the kind of setbacks executives face, and move on to the next problem. But apparently there was more in Feldman's case. By all accounts, he was a self-contained man who didn't share his emotions with anyone -- anyone but his wife, Rosemily, who died of cancer a year ago.

"He got into some difficult business decisions and his personal resources were gone when his wife died," says an acquaintance of Feldman. "He was a decent, able guy who somehow got worked into an emotional corner and decided to burn it all away."

Julian Levine, a long-time friend and associate who became vice president of public affairs of Continental when Feldman took over, said, "He was tired; this thing with TI has taken a lot out of him. But nobody suspected anything like this.

"I really can't speculate on what was in his mind; he was close to Rosemily, but why any human being takes that kind of step is hidden in his personality," he said.

A newcomer to the industry when he became president of Frontier Airlines in 1971, Feldman had worked miracles there, turning the foundering regional carrier into a flourishing, well-managed company fully prepared for deregulation. But he hadn't been able to work the same magic in his 18 months at Continental.

Suffering from the same rising costs and declining traffic as other airlines, Feldman hadn't hit on the right combination for Continental's balance sheet. Continental had an operating loss of $46 million in 1980, $25 million in the first quarter, another loss in the second quarter.

According to some who knew him, Feldman felt that he hadn't spent enough time running the airline. The first 12 months of his tenure was spent pushing the proposed Continental-Western Airlines merger, the next six months fighting the Texas International takeover. As a result, at Feldman's instigation, according to Continental sources, George Warde was hired to take over as president and chief operating officer of the airline, leaving Feldman as chairman.

Feldman was found dead in his Los Angeles office with a bullet wound in the head about 7:35 p.m. Sunday by a security guard. Feldman had worked all day, meeting with other Continental officials, preparing a statement that would tell employes and the public that because of the airline's "inability to assure financing" the employe purchase plan "no longer appears likely under the present circumstances."

Assuming favorable court decisions, the money the banks originally had promised -- up to $200 million -- was essential. It would have allowed Continental to issue 15.4 million new shares of stock to the proposed employe stock ownership plan. The stock issue would have diluted Texas International's 481/2 percent holding in Continental -- effectively blocking its bid for control -- and would have given the employes 51 percent of the airline.

"It was with great sadness that I learned of the death of Al Feldman," Frank Lorenzo, president of Texas Air Corp., the parent company of Texas International, said yesterday. "Mr. Feldman was a man of great honor and integrity and a major figure in our industry. I join with his many friends and colleagues in offering my condolences to his family."

A graduate of Cornell University with a Bachelor of Science degree in Mechanical Engineering, Feldman spent 17 years with Aerojet General Corp., an aerospace contractor, before entering the airline industry.

He reportedly left three suicide notes. The contents were not disclosed but are said to be of a personal nature. He is survived by three children, David, 25; John, 23; and Susan, 20, and two brothers, Herbert and Lester Feldman.