ATLANTA — Delta Air Lines filed a reorganization plan Tuesday that calls for it to emerge from bankruptcy next spring as a stand-alone company worth as much as $12 billion, or slightly more than the combined market value of the nation's two biggest carriers.

The Atlanta-based company also said that its board has formally rejected US Airways' $8.5 billion hostile takeover bid, and its executives joined rank-and-file employees on a full-scale public relations assault against the merger proposal.

"US Airways is the worst of all potential merger partners," Delta Chief Executive Gerald Grinstein said during a conference call with analysts.

Grinstein didn't completely dismiss the idea of a merger with a company other than US Airways, saying later Tuesday that Delta would review any other bids. But he said Delta would not put out a "for sale" sign.

Delta's chief financial officer, Ed Bastian, said in a conference call with reporters Tuesday that Delta so far has not received any other offers.

Delta outlined a five-year business plan. Its advisers estimated that a reorganized Delta will have a consolidated equity value of $9.4 billion to $12 billion and that Delta's unsecured creditors would recover roughly 63 percent to 80 percent of their allowed claims.

The high end of the equity value Delta is projecting would be more than the $11.9 billion in combined market value of AMR Corp.'s American Airlines and UAL Corp.'s United Airlines.

Delta's existing stock would be wiped out under the plan and creditors generally would receive distributions of new Delta common stock to settle their claims. Delta so far has not decided whether to give creditors any cash.

US Airways' offer included $4 billion in cash and 78.5 million shares of US Airways stock.

Tempe, Ariz.-based US Airways Group Inc. issued a statement saying it remains committed to its merger proposal, and it added it believes its proposal, including $1.65 billion in anticipated cost savings, provides more value than Delta's plan.

"We remain a disciplined and determined bidder for Delta," US Airways Chief Executive Doug Parker said.

An official with knowledge of US Airways' plans, who spoke on condition of anonymity because of the sensitivity of the talks, said Monday that US Airways was willing to increase its offer if Delta could justify it is worth more. But Delta said Tuesday it believes flying solo is the best proposal for everyone involved.

Creditors must now vote on whether to approve Delta's reorganization plan or any competing plan that may be filed with the court. The plan also must be approved by the court.