Airlines found an opportunity to raise fares this week after the government suspended a federal security fee, but investors are likely to take the news in stride.

To help aid the airline industry, Congress gave carriers a four-month reprieve from having to charge up to $10 in security fees per ticket. Major airlines opted to pocket the money they previously would have charged customers for fees, so ticket prices will largely remain the same for travelers.

Yet given the fact that airline stocks have doubled over the past two months, analysts don't expect the fare news to give stocks much of a boost.

"Considering the two-month return profile of AMR, Continental and Delta Air Lines has already exceeded that threshold, impatient investors may very well head for the exits. And who could blame them?" said J.P. Morgan analyst Jamie Baker in a research report on Tuesday.

AMR unit American Airlines was the first to opt to keep fares at current levels. After that, every major carrier, even Northwest Airlines ( NWAC), which has a history of playing spoilsport , matched American.

On Tuesday afternoon, the Amex Airline index was up 0.2%, with only AMR and Delta keeping the index in the green. Continental, Northwest, UAL ( UALAQ) and Southwest ( LUV) were all lower.

The Justice Department said it is examining the carriers' de facto fare increase for signs that it violates antitrust law, but some analysts expressed skepticism.

" Justice is just looking to rattle everyone's cage. You have unprecedented losses in this industry," said Kent Krause, managing partner at Speiser and Krause, which specializes in aviation law. "I think they'd be hard pressed to be successful if they're really serious about pursuing this. In light of the issues facing the industry, and where the $10 increase is really covering the reduction in security fees, I think they'll probably drop the matter."

Thomas Nulty, airline veteran and partner in Corporate Solutions Group, took a positive view of the fare news. "The vast majority of this fare increase will sink to the bottom line," he said.

J.P. Morgan's Baker, meanwhile, expressed caution. "Presuming said profit levels do materialize within two years and the market values profitable airlines as it often has at eight to 10 times forward earnings per share, it is difficult to envision anything greater than a doubling of current equity values."

Baker expects an industry loss of $600 million in the third quarter, and a loss of $200 million in the fourth quarter, the lowest loss since the second quarter of 2001. In his eyes, a cyclical recovery is just around the bend, but the stock recovery may have left the gate already.