Delta Air Lines, the nation's No. 3 carrier, is expected to seek Chapter 11 protection as soon as tomorrow after a long fight to avoid bankruptcy.

Delta would become the third major airline to seek bankruptcy protection since the Sept. 11 terrorist attacks, joining United Airlines and US Airways.

Delta's anticipated filing in U.S. Bankruptcy Court in New York is not expected to have an immediate effect on flight schedules or passengers.

The company, which already has slashed costs, will continue flying while restructuring under the potent protections of federal bankruptcy law, according to three people outside the company familiar with preparations. The sources declined to be identified because of the legal sensitivity of the matter.

Delta spokeswoman Chris Kelly said yesterday the company "has made no decisions at this time regarding a Chapter 11 filing." Delta's battered stock closed yesterday at 85 cents, down 23 percent on reports of the impending filing. Company directors would have to vote to authorize a bankruptcy filing.

Atlanta-based Delta has warned for months in securities filings that it has been at risk of bankruptcy. With the cost of jet fuel at unprecedented levels, Delta is fighting a losing battle against cash drain. Burdened with $26 billion in debt and heavy losses, Delta has been burning through at least $2 million a day in cash.

Delta also is fighting the clock. On Oct. 17, changes in the federal bankruptcy law will make Chapter 11 bankruptcy reorganizations harder and more expensive for companies to file.

Unless it is in Chapter 11 protection, Delta would owe mandatory payments of $135 million to its pension plan on Oct. 15.

Led by CEO Gerald Grinstein, who succeeded former CEO Leo Mullin in January 2004, Delta has sought for 20 months to restructure outside of bankruptcy.

As a result, Delta's bankruptcy case promises to be well organized. Since last year, when it narrowly averted Chapter 11, Delta has been working with law firm Davis Polk & Wardwell and financial advisers on a possible bankruptcy filing. A group of Delta's large unsecured creditors has been working with adviser Saybrook Capital and law firm Skadden Arps.

Delta now is close to finalizing or has finalized $1.7 billion in "debtor-in-possession" bankruptcy financing in a package led by General Electric, say two of the sources with knowledge of the airline's preparations. GE declined comment.