CHARLOTTE, N.C. -- A leading airline investor has bought 5.1% of AirTran ( AAI), a carrier with cost levels among the lowest in the airline industry and shares that are trading near five-year lows. Boston-based hedge fund PAR Capital Management bought 4.7 million AirTran shares, according to a 13G filing Tuesday. A 13G indicates that the acquiring party is a passive investor and does not intend to exert control. PAR "is in and out of airline stocks when they believe (the stocks) are cheap, and among the low-cost carriers AirTran is probably the most attractive," said Calyon Securities analyst Ray Neidl. During the bankruptcy of US Airways ( LCC), PAR was among the most successful investors, getting in early and becoming, at one time, the airline's largest shareholder. With US Air, PAR bought 11 million shares at $15 and another 2.75 million shares around $40, then sold 6.75 million shares at roughly $36 and 6.5 million shares around $58. US Airways traded Tuesday around $12. Ed Shapiro, PAR Capital vice president, has a seat on the US Airways board. He declined to comment Tuesday. "PAR has an excellent track record in their airline investments," says FTN Securities analyst Mike Derchin. "They have followed the industry closely for years and tend to take a longer term, value-oriented view toward the shares." He says PAR was "almost perfect on its 'buy low, sell high' trade on USAirways." AirTran will report earnings on Jan. 29. In the third quarter, the carrier reported cost per available seat mile of 5.92 cents. There has been little consolidation chatter involving AirTran, although Derchin suggests that it could conceivably become a target for Southwest ( LUV). After all, if there are to be transactions or consolidation in the airline industry, it may be unreasonable to assume that the action will be entirely confined to the legacy carriers. In fact, in a joint announcement Tuesday, Lufthansa said it has completed its acquisition of 19% of low-cost carrier JetBlue ( JBLU). "With the conclusion of the financial transaction, Lufthansa and JetBlue will begin exploring innovative commercial arrangements designed to benefit both airlines and their customers," the carriers said.