Typically, in each class of creditors Delta's plan would have to be approved by holders of two-thirds of the claims and a majority of the number of individual creditors, said New York bankruptcy lawyer William Rochelle. If a class is not impaired — that is, if they are guaranteed of getting all of their money back no matter what — they generally don't get to vote, Rochelle said.

If one or more classes of creditors do not approve the plan, Delta could still confirm the plan through a so-called cramdown, a maneuver in which it must show the court that the dissenting class will receive more under the plan than it would under a Chapter 7 liquidation, Rochelle said. The company also would have to show that any subordinate class, such as shareholders, would get nothing in the way of recovery under the reorganization plan, Rochelle said.

Delta already has met that second test because its plan calls for current shares of the company to be wiped out.

If a competing plan were filed, creditors would vote on each individually. There have been bankruptcy cases where two competing reorganization plans were approved by creditors; in such a case, a judge decides which plan is confirmed after holding a hearing to determine which plan is in the "better interest" of the creditors.

"Bankruptcy is like anything else," Rochelle said. "Money talks at the end of the day."

Ultimately, the unsecured creditors committee in the bankruptcy case will play a key role in determining Delta's fate. The committee has not said whether it will support Delta's plan, US Airways' plan or any other offer to buy Delta that may come in. A lawyer for the committee, Daniel Golden, did not immediately return a call Tuesday seeking comment. Rochelle said Delta would likely wait to hear from the creditors committee about its views before soliciting votes on its plan.

Delta also said Tuesday that its board has unanimously rejected US Airways' unsolicited offer, disclosed Nov. 15. Delta employees held rallies at airports serving several cities, including Cincinnati, Boston and Columbia, S.C., protesting US Airways' bid; Delta executives attended a similar rally in Atlanta.

After falling for most of the day, US Airways shares bounced back and rose $1.70, or 3.1 percent, to close at $57.50 Tuesday on the New York Stock Exchange, putting the value of its bid for Delta at $8.5 billion.

Delta said it believes the US Airways deal is not likely to gain regulatory approval. It also cited as obstacles: overwhelming labor issues and "flawed economic assumptions."