ATLANTA - Delta Air Lines Inc.'s new shares began their first trading day on the New York Stock Exchange yesterday at a price below the company's initial projection.

Delta's chief financial officer, Ed Bastian, said he was pleased with the carrier's having the second-highest market capitalization in the industry, even as one analyst predicted that the ranking would be short-lived.

The Atlanta-based company's shares opened their first public trading day since Delta exited bankruptcy Monday at $21.75. That pegged Delta's initial market value at $8.7 billion, based on the 400 million shares Delta planned to issue. All of those shares were outstanding, but, as of yesterday afternoon, about 150 million shares had not been issued because of unresolved claims with creditors, a Delta spokesman said.

Delta shares fell from the opening trade to finish the day at $20.72, dropping Delta's market value to $8.3 billion.

The company's shares were being traded under its familiar DAL ticker symbol.

The initial market value was short of the $9.4 billion to $12 billion that Delta had projected in its reorganization plan.

The opening stock price was also short of the $9.8 billion that US Airways Group Inc., of Tempe, Ariz., had offered for Delta. The hostile-takeover bid was defeated in January.

But Bastian, Delta's chief financial officer, said he was excited about Delta's prospects, especially considering that its market value was second-highest in the airline industry. Dallas-based Southwest Airlines Co. has the highest, at $11.3 billion.

"That's an affirmation of the job we've done," Bastian said.

Even so, one analyst at Prudential Equity Group L.L.C., Bob McAdoo, said in a research note yesterday that Delta's stock was overvalued and trading at levels, in comparison with its peers, that were unsustainable. His firm initiated an "underweight" rating on Delta's new stock and a $14 price target.

"We will review our rating once Delta's valuation is more consistent with the other legacy carriers," McAdoo wrote.

Delta exited bankruptcy Monday after a 191/2-month reorganization that saw it shed billions of dollars in costs. Its previous shares were canceled when it left bankruptcy.

Delta entered Chapter 11 on Sept. 14, 2005, amid high fuel prices and the burdens of high labor and pension expenses. Delta significantly reduced its labor and pension costs while under court protection.

Chief executive officer Gerald Grinstein, who bought 1,000 shares of new Delta stock yesterday at $21.75 a share, pressed a button to ring the closing bell from the floor of the NYSE. He then banged a gavel to signal the end of the session.