The battle to carve out territory in Hawaii’s skies is reaching new heights with Southwest’s announcement today that it will start daily San Diego service and add more daily interisland seats.

Southwest will begin once-daily service between San Diego and Kahului on April 14, and once-daily service between San Diego and Honolulu on April 20. The carrier will offer introductory fares of $129 each way on these routes for travel between the April start dates and June 4. The fare sale was scheduled to start at 3 a.m. today and will end at 11:59 p.m., subject to availability.

Maui’s expanded service brings the count of daily flights between Honolulu and Kahului to six, up from four. Southwest also is temporarily adding service between Honolulu and Hilo for the Merrie Monarch festival, bringing the count to six flights each way daily from April 15 to 18 and seven flights each way April 19. The interisland expansion will trigger a Nov. 4 sale in select interisland markets with fares on limited seats dropping to $29 each way for travel from Nov. 11 to March 4.

The 700-seat trans-Pacific addition brings Southwest’s trans-Pacific service to 28 daily flights with about 4,900 seats. In comparison, competitor Alaska Airlines has 62 daily flights and nearly 10,000 seats.

Both carriers trail behind Hawaiian Airlines’ trans-Pacific service, which averages 60 daily flights and 13,590 seats between Hawaii and 13 mainland gateway cities, and 15 daily international flights with 4,275 daily seats, for a trans-Pacific total of 75 daily flights and 17,865 seats.

Southwest also has brought its interisland service to 38 flights and 6,650 seats a day.

While growing, Southwest remains a significantly smaller player in the interisland market than Hawaiian, which flies 160 to 180 flights a day between the islands, based on the season. Hawaiian’s Boeing 717 planes have 128 seats, so that’s between 20,480 and 23,040 interisland seats a day, depending on the time of year.

Today’s expanded- service announcements point to Southwest’s commitment and bullishness on Hawaii, especially given that it still hasn’t gotten relief from the FAA’s grounding of Boeing 737 Max planes after crashes in Indonesia and Ethiopia. Southwest doesn’t fly Max planes in Hawaii, but the groundings and resulting flight cancellations on the mainland have had significant operational and financial impacts across its network.

During a Thursday earnings call, Southwest Chairman and CEO Gary C. Kelly said Southwest’s “2020 market priorities will continue to be Hawaii, which is going extremely well.”

Kelly said the carrier’s Hawaii flights were performing well.

“So we’re not backing off (Hawaii). It may have to pace a little bit, depending upon the Max,” he said.

During the same earnings call, Southwest President Tom Nealon said demand for Hawaii service “continues to be very, very strong, and our load factors (seats occupied) continue to exceed our system average. The demand for our interisland service is also very strong. And this also includes a very strong mix of local customers, which we’re thrilled about.”

Nealon added that Southwest’s Hawaii intentions include planning for “additional flights in 2020 to continue building off our initial success.”