Small interisland flight company Mokulele Airlines plans to more than double its service by the end of the year following a recent investment from prominent local mechanical engineer Dorvin Leis.

Leis acquired a minority stake in the carrier for an undisclosed price described only as more than a few million dollars, according to the airline.

The investment, agreed to in principal earlier this year, allows Mokulele to proceed with adding three new nine-passenger planes over the next three months to its current fleet of two older nine-passenger aircraft.

Mokulele CEO Bill Boyer said the company expects to add five more of the $2 million planes next year to make a fleet of 10.

"I'm in Atlanta right now with Dorvin," Boyer said yesterday by phone. "We're buying airplanes."

The investment by Leis, founder and chairman of the state's largest mechanical contractor Dorvin D. Leis Co., is behind the latest round of growth by Mokulele amid an intense battle for market share dominated by Hawai'i's larger interisland carriers engaged in cut-throat fare discounts since low-cost interisland carrier go! launched service last year.

Mokulele was founded on the Big Island in 1998 primarily as a tour and on-demand passenger carrier called Mokulele Flight Service. Boyer bought the Kailua, Kona-based company in 2005 and a year later obtained approval to begin scheduled passenger service. Boyer expanded Mokulele's fleet from two to five nine-passenger Piper Chieftains.

The company primarily flew between Kahului, Maui and Kona, but also served other Neighbor Island airports. Earlier this year, Mokulele began service to Honolulu from Maui and Moloka'i through a revenue-sharing arrangement with go!, under which consumers can book flights through go! on Mokulele planes operating as go!Express.

Mokulele also is replacing its fleet of twin-engine Piper Chieftains with more powerful and comfortable turboprop Cessna Grand Caravan 208B planes featuring leather seats, video displays, and weight limits that allow passengers to bring more baggage aboard.

Currently, Mokulele is using two Cessnas to operate 24 flights a day. The airline's older planes are not in use, and are for sale.

On Oct. 1, Mokulele is slated to begin daily service between Ho-nolulu and Lana'i.

Boyer said the company's goal with 10 planes is to have one departure every 35 minutes.

"Our goal is to make the interisland flying experience right for everyone," Boyer said.

As part of the expansion plans, Mokulele intends to move most of its office operations from Kona to Downtown Honolulu, and is adding about 40,000 square feet of hangar space at Honolulu International Airport to service its aircraft and possibly private aircraft.

Reach Andrew Gomes at agomes@honoluluadvertiser.com.