CHARLOTTE, N.C. ( TheStreet) -- Delta ( DAL - Get Report) and US Airways ( LCC) both reported rare first-quarter profit, a sign that the airline industry may have found the formula for consistent financial performance.

Historically, airlines lose money in the first quarter, a slow travel season. But this year, among the major carriers only United ( UAL - Get Report) is expected to report a first quarter loss.

"A key benefit from a consolidated industry is that we now see a much stronger correlation between revenue and fuel," said Delta President Ed Bastian, in a prepared statement. "So while we are seeing some revenue softness, we are also benefiting from lower fuel costs, allowing us to continue our path of margin expansion even in a sluggish economic environment."

US Airways said first-quarter net income excluding items was a first-quarter record $55 million, or 31 cents a share. Analysts surveyed by Thomson Reuters had estimated 28 cents. In the same quarter a year earlier, excluding items, the carrier lost $22 million, or 13 cents a share. Revenue rose 3.5% to $3.4 billion, in line with estimates.

Including items, the carrier reported a net profit of $44 million, or 26 cents a share, compared with $48 million, or 28 cents, a year earlier.

The carrier credited "a strong demand environment and record passenger load factors" for its strong results. Revenue per available seat mile rose 2.2% to a record 15.78 cents, as consolidated capacity rose 1.3%. On the cost side, mainline cost per available seat mile excluding fuel and special items rose 0.7% to 8.77 cents. Including fuel and items, mainline CASM was 13.82 cents.

The carrier said its pending merger with American ( AAMRQ.PK) is expected to close in the third quarter.

Delta said its net profit was $85 million, or 10 cents a share. Analysts had estimated 6 cents. Revenue rose 1% to $8.5 billion, in line with estimates. Including $78 million in special items, net income was $7 million, or 1 cent a share.

"Our results represent Delta's strongest March quarter financial and operational performance in over a decade," said CEO Richard Anderson in a prepared statement.

Passenger revenue per available seat mile rose 4.1%, led by an 8.1% gain in the trans-Atlantic and a 4.9% domestic gain. Mainline unit revenue gained 5.5% while regional unit revenue gained 1.8%. On the cost side, cost per available seat mile excluding fuel and special items rose 5%, driven by the impact of capacity reductions, wage increases and operational and service investments. Fuel expense for the quarter declined by $78 million.

Delta said it anticipates that April unit revenue will decline. "We are taking actions to mitigate the decline in close-in demand we saw in the last part of March, and we expect the impact of the sequester, combined with a softening of leisure demand, to result in a 2% -3% percent decline in April's unit revenues," Bastian said.

In the second quarter, Delta estimates an operating margin between 9% and 11%.

-- Written by Ted Reed in Charlotte, N.C.

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