Less than two weeks after Mesa Air Group Inc., parent of interisland carrier go!, filed a lawsuit against Mokulele Airlines to collect fuel payments, Mokulele has fired back with a suit of its own, accusing the Phoenix-based carrier of a breach of contract and unfair competition in the Hawaii market.

The lawsuit was filed in U.S. District Court in Hawaii yesterday, with the amount in controversy exceeding $75,000, although no specific dollar figure was given. It is Mesa's fifth lawsuit involving an isle airline or industry employee since entering the Hawaii market in June 2006.

The filing claims that Mesa used unfair anti-competitive practices to drive Mokulele out of business, and interfered in a contract announced last month between Mokulele and Indianapolis-based Republic Airways to operate four 70-seat Embraer 170 jets in the interisland market. The expansion is an effort to fill capacity left by the shutdown of Aloha and ATA airlines this spring.

The filing also claims that Mesa breached a code-share agreement entered into in February 2007, under which Kona-based Mokulele operates three nine-seat Cessna 208B Grand Caravans under the go!Express name to serve to serve smaller airports including Kapalua, Maui; Lanai and Molokai.

Mokulele CEO Bill Boyer declined to comment on the ongoing litigation. Mesa Chief Executive Jonathan Ornstein did not return a call for comment.

Mesa's “;misconduct is part of a plan to run local airlines out of business,”; the lawsuit states, so that it will be one of only two main airlines in the interisland passenger market, along with Hawaiian Airlines.

The lawsuit states that upon learning that Mokulele would be partnering with Republic, Mesa “;set its predatory sights”; on Mokulele, embarking on a “;scheme to forestall competition.”;

In a lawsuit filed in U.S. District Court in Arizona on Oct. 20, Mesa claimed that Mokulele failed to pay $171,819.94 for June fuel costs and $219,520.16 for July under the code-share agreement. Mesa stopped selling fuel to Mokulele on Oct. 15.

“;As everybody knows, at Mesa, we have our own issues,”; Ornstein said at the time. “;We are not in the position to be another airline's bank. Something like this happens and you really feel like you are getting taken advantage of.”;

Mokulele and Mesa have a six-month notification period to terminate the go!Express service, Ornstein said. Mokulele said in the lawsuit that it has “;reasonable grounds to believe that Mesa Airlines will breach the code-share agreement.”;

Mokulele claims that Mesa charged unreasonable below-cost fares that put undue pressure on the airline. It also claims that Mesa shut down its reservations system so Mokulele could not service go!Express passengers, as well as refusing to allow Mokulele to operate its portable counters at the Honolulu International Airport in space that Mesa had leased but previously allowed Mokulele to use.

The suit also claims that Mesa has failed to pay Mokulele revenues due under the code-share agreement by increasing its reimbursable expenses retroactively to March 1, 2008. Mesa also purposely overbooked its go!Express flights and refused to provide assurance for payment to accommodate stranded passengers, Mokulele said.

Go! has lost $42.1 million since beginning service in June 2006, partly attributable to a $5.6 million increase in legal and consulting fees due to lawsuits involving Hawaiian and Aloha airlines. Mokulele is privately held.

Mesa agreed in April 2008 to pay Hawaiian Airlines $52.5 million in damages to settle a lawsuit regarding the carrier's misuse of confidential and proprietary information obtained in 2004 during Hawaiian's bankruptcy.

Mokulele, which Boyer bought in 2006, operates six nine-seat Cessna 208B Grand Caravans, as well as one Cessna Grand Caravan cargo freighter, with another expected to enter service in less than a month.

Mesa operates five go! 50-seat CRJ-200 aircraft in Hawaii, with the fifth used as a spare.