ATA Airlines Inc. said yesterday it plans to add 21 weekly Mainland-to-Hawai'i flights next summer, boosting its capacity by 14 percent.

ATA will have 171 weekly departures and arrivals serving Hawai'i, the West Coast and Las Vegas, bringing the Indianapolis-based discount carrier closer to the level of Hawai'i's top airlines. United Airlines, American Airlines and Hawaiian Airlines each operate more than 200 flights a week from the Mainland.

Starting in June, ATA will begin flying between Oakland, Calif., and Kona on the Big Island and Lihu'e, Kaua'i; and between Las Vegas and Maui.

The airline also will add a daily flight between Oakland and Honolulu, doubling its service on that route.

"I think it shows that the demand for Hawai'i continues to be very strong," said ATA spokesman Rick Hightower.

ATA, founded in 1973, is a discount airline serving Chicago; New York; Washington, D.C.; Dallas/Fort Worth; Hawai'i; and Cancun and Guadalajara, Mexico.

The airline, which emerged from bankruptcy protection in February, has a code-share agreement with Southwest Airlines. Southwest does not fly to Hawai'i, but many of its customers travel to the Islands on ATA, said Hightower.

"That's a golden opportunity that we want to take advantage of," Hightower said.

Marsha Wienert, state tourism liaison, says ATA's expansion could boost travel for first-time visitors to Hawai'i.

Much of Southwest's business comes from eastern states, which is a growth area for Hawai'i's tourism market, said Wienert.

"I think it shows that Hawai'i's brand is very strong," she said.

ATA's expansion comes as several major U.S. carriers have increased their capacity to Hawai'i during the past year.

U.S. Airways, which merged with America West Airlines, began flying from Phoenix to Honolulu and Maui last year while United added 21 weekly departures from the West Coast last summer, bringing its total to 227 weekly flights to Hawai'i.

ATA's new flights will compete directly with Aloha Airlines, which offers nonstop service between Oakland and Honolulu and the Neighbor Islands.

Aloha, which flies 106 weekly departures from the West Coast, had no comment on ATA's expansion.

Reach Rick Daysog at rdaysog@honoluluadvertiser.com.