Delta Air Lines (DAL) said Monday that it may have to seek bankruptcy protection if it doesn't get significant wage cuts from pilots, the first time the struggling carrier has publicly linked the two issues in a regulatory filing. Its shares fell more than 15 percent.

The Atlanta-based company has said repeatedly that it would fight to avoid bankruptcy and has been cautious in the words it uses when discussing that possibility. Asked about it at Delta's annual shareholder meeting last month, chief executive Gerald Grinstein said only that bankruptcy would be undesirable.

But in a quarterly report with the Securities and Exchange Commission (search) on Monday, Delta said in part: "If we cannot achieve a competitive cost structure, regain sustained profitability and access the capital markets on acceptable terms, we will need to pursue alternative courses of action... including the possibility of seeking to restructure our costs under Chapter 11."

Delta has said the need for a competitive cost structure refers to reducing pilot wages.

Spokesman Anthony Black said that while it is the first time the specific language regarding bankruptcy has been used in a public filing, Delta has not changed its position. He also noted that Delta is seeking to reduce cuts beyond pilot wage concessions, including through increased productivity and customer service improvements.

"It's an option," Black said of bankruptcy. "It's not anything we see in the foreseeable future, but it's out there."

In trading on the New York Stock Exchange (search), shares of Delta fell 84 cents, or 15.6 percent, to close at $4.54, their lowest close on record since 1980.

Ray Neidl, an analyst with Blaylock & Partners in New York, said the language in the filing suggests Delta is guarding itself and making sure it warns people about the possibility of bankruptcy. He said the key to Delta's survival is clear.

"It's strictly dependent on the pilots," Neidl said. "They can avoid bankruptcy if they get the cost cuts. If they don't, they'll have to go into bankruptcy."

In a statement the pilots union said it is willing to assist Delta in cutting costs and has attempted to negotiate with the company along those lines.

The company is seeking a 30 percent pay cut from pilots, who are offering only 9 percent and to forego a 4.5 percent raise they were to have received earlier this month. Talks have been on-again, off-again over the past year.

Delta, the nation's third-largest airline, has lost more than $3 billion and laid off 16,000 employees in the last three years. In the first quarter, it lost $387 million.