AirTran Airways will depart Atlantic City International Airport for good in January, leaving the local airport with only one primary carrier, Spirit Airlines.

AirTran has run a twice-daily route to its Atlanta hub since June 2009, when it entered an agreement with airport operators that subsidized flights that did not generate enough passenger revenue.

The subsidy agreement, which provided $2.5 million in 2009 and $1.5 million in 2010, expires in September.

AirTran said in a statement Monday that it could no longer support service to the airport and three others nationwide “in light of the realities of the challenging economic environment and sustained high fuel prices.”

A representative of AirTran could not be reached Monday afternoon for additional comment. Its last day of service at Atlantic City International will be Jan. 6.

The announcement Monday is a setback for the airport in Egg Harbor Township as it seeks to increase passengers and service to more airports across the country.

Since 2000, Continental, U.S. Airways, Delta Air Lines and West Jet have ended service to Atlantic City.

Spirit Airlines is the airport’s main passenger carrier and transports the majority of airport passengers.

Trips to Atlantic City by air represent a small portion of overall trips — about 1 percent, a 2010 report by airport operator the South Jersey Transportation Authority shows. That represented 292,019 trips to the resort in 2010, a 22 percent increase from 2009, the report states.

Trips via more widely used modes of transportation — such as cars and casino buses — declined in that time period.

Visitors who arrive by air are desirable for several reasons, said Brian Tyrrell, a professor of hospitality and tourism at The Richard Stockton College of New Jersey.

“They tend to stay longer and spend more, and it gives us the opportunity to cultivate some visitors from a region that might not otherwise come,” he said.

Southwest Airlines acquired AirTran in May, although the airlines are operating separately and integrating gradually.

Airport officials have said they have not yet spoken to Southwest.

In 2009, the SJTA sought airlines that would connect the local airport to a national circuit of flights, to boost airport passengers and aid the region’s tourism economy.

In an agreement with AirTran, the authority entered into a “risk abatement agreement” offering millions of dollars in subsidies on the route from Atlantic City to Atlanta.

In February, that agreement was extended until September, guaranteeing as much as $1.4 million in subsidies this year.

AirTran had previously flown to Orlando, Fla., but canceled that route in July 2010.

On Monday, AirTran also announced it was discontinuing operations at Asheville Regional Airport in North Carolina, Quad City International Airport in Illinois and Newport News Williamsburg International Airport in Virginia.

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