The state Department of Transportation is building a $40 million to $45 million structure under Gate 6 at the Daniel K. Inouye International Airport that was meant to provide operating space for Island Air, but that space will now be left vacant in the wake of the airline’s bankruptcy.

Tim Sakahara, spokesman for the Transportation Department, said state officials are in the process of scaling back on that project to leave the 24,000-square-foot space as an unfinished shell, which will reduce the cost of construction somewhat.

Transportation officials don’t know yet exactly how much the state will save by reducing the scope of the project, but “it will be several million dollars less,” he said.

“The construction of the project will continue,” Sakahara said. “It’s just that now, when an airline or a tenant is determined, then they’ll go ahead and make the necessary improvements that would be needed.”

Island Air filed for reorganization in bankruptcy court on Oct. 16 and ended flight operations Nov. 10. It filed for liquidation under Chapter 7 bankruptcy on Nov. 15.

Island Air had been operating from the old interisland commuter terminal at the airport, but the state urgently needed to move its operation, along with Mokulele Airlines, so that the old terminal building can be demolished.

The state needs to tear down the old low-rise commuter airline terminal next to the interisland terminal to clear the site for a planned new Mauka Concourse. That new concourse will provide badly needed new gates at the crowded airport.

Construction of that new $220 million concourse has been stalled for well over a year while transportation officials figured out what to do with Island Air and Mokulele, which still operates from the old commuter terminal.

The solution transportation officials adopted was to move Island Air to the area below Gate 6, and move Mokulele to an area near the United Airlines cargo facility. The state hopes to have Mokulele moved and operating from its new location by March or April, Sakahara said.

Mark Dunkerley, president and chief executive officer of Hawaiian Airlines, said the company supported the Department of Transportation’s effort to take advantage of the unused space under Gate 6 to accommodate Island Air.

“I think it’s unfortunate that Island Air went bust before they could use that space, but if there’s another carrier that wants to come into the market, there will be some space ready for it,” Dunkerley said.

Airport expenses including construction costs are paid with fees charged to users, and Hawaiian Airlines now pays about 40 percent of the total fees collected by the airport, according to company officials.

Work on the new concrete-and-glass structure meant for Island Air began in July at ground level below Gate 6 in the Diamond Head terminal. Gate 6 and that area of the terminal are used by United Airlines, Sakahara said.

The original design called for ticket counters, a baggage claim area, a security checkpoint, and a parking and a drop-off area for passengers, but all of those features have been dropped from the project, he said.

“Essentially, what the area will be is one large hold room now,” he said. It will have lighting, restrooms, concession space, an escalator, air conditioning and fire sprinklers, he said, and will be large enough to hold about 500 passengers.

Sakahara said contractor Hensel Phelps Construction Co. was using double crews and working seven days a week to complete the structure so that Island Air could move to the new site quickly, but that accelerated pace is no longer necessary since Island Air won’t be moving in.

Sakahara said the new structure should be completed next spring, but it is still unclear what the space will be used for, or who will use it.

“Eventually we’re confident this space will be used,” Sakahara said. “It’s just a matter of determining who and when.”