NEW YORK (Bloomberg) — US Airways Group Inc. and AirTran Holdings Inc., the parent of AirTran Airways, posted third-quarter net losses as fuel expenses rose and new airport-security rules damped travel demand.The loss at US Airways, the seventh-largest US carrier, was $78 million, and included costs of $179 million linked to fuel and its 2005 merger with America West. AirTran’s $4.3 million loss compared with a year-earlier profit of $1 million.

“There are two themes to this reporting season as we see it,” UBS Securities analyst Kevin Crissey wrote in a research note today. Demand looks stronger this quarter than last quarter, and “low-cost carriers are struggling and slowing growth”, he wrote.

US Airways and AirTran, which are both low-cost airlines, joined JetBlue Airways Corp. and Alaska Air Group Inc. in reporting losses in what has traditionally been the industry’s strongest quarter. AMR Corp.’s American Airlines, Continental Airlines Inc. and Southwest Airlines Co. all posted profits.

US Airways and AirTran spent more on fuel, their biggest expense, even though prices started sliding in August. Security restrictions imposed that month after the UK broke up a terrorist plot against jetliners cost US Airways as much as $40 million in lost revenue.

AirTran said it also experienced a third-quarter sales slowdown because of the security rules, which included a ban on liquids in carry-on baggage. Like JetBlue, it’s paring its previously announced expansion plans.

US Airways’ loss was 88 cents a share, the Tempe, Arizona- based airline said in a statement. Sales were $2.97 billion. Excluding $179 million in costs tied to locking in fuel prices in advance and merging operations, the carrier had a profit of $101 million, or $1.09 a share.

“This compares favourably with our $1.03 and the Street’s $1.01,” Crissey wrote in a research note.

US Airways expects to report a profit in the “seasonally difficult fourth quarter”, chief executive officer W. Douglas Parker said in the statement.

US Airways was created when it exited bankruptcy protection and merged with America West Holdings Corp. in September, 2005. It didn’t provide combined results for the year-earlier full quarter.

Excluding one-time costs, US Airways was expected to earn $1.10 a share by Ray Neidl, a New York-based analyst at Calyon Securities Inc. who’s among the top-rated analysts for accuracy by StarMine Corp.

Airtran’s loss was five cents a share, compared with net income a year earlier of $1 million, or 1 cent, the Orlando, Florida-based company said in a statement. Analysts expected the carrier to post a profit.

A 30 percent increase in revenue to $487.3 million couldn’t offset a 52 percent jump in spending on fuel to $190.7 million.

“We began to see a slowdown in the end of August” as the new airport-security regulations took effect, chief executive officer Joe Leonard said in the statement. “We have begun to see a return to more normal booking levels in mid-November.”

The results trailed Neidl’s profit estimate of two cents a share and the 3-cent average estimate in a survey of 11 analysts by Thomson Financial.

The third-quarter results included a non-cash charge of $1.5 million, or two cents a share, related to a free-ticket promotion.