Delta Air Lines Inc.’s third-quarter profit beat analysts’ estimates, buoyed by domestic travel, and the carrier forecast gains in revenue in the year’s final period.

Earnings excluding some items were $1.20 a share, the Atlanta-based carrier said in a statement today. That surpassed the $1.18 average of 18 estimates compiled by Bloomberg. Sales increased 7 percent to $11.2 billion, compared with an average projection of $11.1 billion.

The fourth-quarter operating margin will be 10 percent to 12 percent, the carrier said.

Delta is the first major airline to report earnings for the quarter, as the six biggest U.S. carriers are expected to report combined profit of $3.9 billion excluding some items, analyst estimates compiled by Bloomberg show.

“For the December quarter, the overall revenue environment remains solid, with unit revenues expected to increase by 0 percent to 2 percent,” Ed Bastian, Delta’s president, said in the statement. “We are on track to produce another quarter of good top line growth, margin expansion and free cash flow.”

The airline boosted its domestic capacity by almost 5 percent last quarter while chasing high fares, Bloomberg Intelligence analyst George Ferguson wrote in a note Oct. 7. He said in a later note that international markets “appear overcrowded.”

Delta is furthest along among the major U.S. carrier in its post-merger integration, after combining with Northwest Airlines in 2008. The carrier has benefited from a domestic market with higher passenger yields, 16 cents a mile, than any other global region, according to Bloomberg Intelligence data.

Adding Capacity

Delta has been trying to capitalize by adding capacity in select markets, including continuing to build an Asian hub in Seattle and growing aggressively in Latin America, where it has long lagged behind American Airlines Group Inc. and United Continental Holdings Inc.

Delta added 20 percent more capacity in Latin America this year through September, according to an Oct. 2 statement.

The carrier’s shares fell 1.3 percent to $32.38 yesterday in New York. They have gained 18 percent this year through yesterday, as American climbed 26 percent and United rose 12 percent.

To contact the reporter on this story: Michael Sasso in Atlanta at msasso9@bloomberg.net. To contact the editors responsible for this story: Ed Dufner at edufner@bloomberg.net.

Photo Credit: A Delta Air Lines airplane is parked at Seattle-Tacoma International Airport in Seattle. Ted S. Warren / Associated Press