In yesterday’s discussion about Hawaiian’s planned replacement for the B717 on interisland trips, I mentioned how Southwest uses a model that flows airplanes from the mainland into the interisland operation. Today, I’m going to look more closely at how that is constructed.

Southwest started flying interisland in April of 2019 with the B737-800, but that was always a stopgap until the MAXs were an option. The first MAX went on interisland flying in June 2021, and the last -800 flew in April 2022. It’s been all MAX since that time.

Southwest peaked its operation in summer of 2023 with 64 daily interisland flights, less than half what Hawaiian was doing but with a bigger airplane. Starting in April 2025, Southwest cut its operation in the state, and that saw peak day departures drop to 50. It has stayed there pretty much ever since.

The Southwest and the Hawaiian networks are almost identical. Both airlines fly from Honolulu to Līhuʻe, Kahului, Kona, and Hilo. They also both fly from Kahului to Kona and Līhuʻe. Hawaiian alone flies Kahului to Hilo along with Kona to Līhuʻe, but those arenʻt very frequent with the former operating 6x weekly this summer and the latter 1x daily. Overall, Hawaiian just has a lot more flights than Southwest on each route. For example, on the key Honolulu – Kahului route, Hawaiian has 19 daily compared to Southwestʻs eight.

Despite the differences, thereʻs enough similarity here to make looking at Southwestʻs structure useful for how Hawaiian could consider a similar model. For this, I took a look at Friday, June 19 for more detail.

That day, Southwest had 14 different aircraft operating the 50 flights. But itʻs how they flow thatʻs most interesting. Thanks to Claude’s design work, here is how it looks.

^{Data via Cirium}

We have some airplanes like N8775Q and N8728Q that just fly around the islands all day long. Others come in from the mainland and then do some interisland flying while some start interisland and then head off to the mainland. But even those that fly around the islands all day donʻt stay for long.

In this group, of the airplanes starting their day in the islands, two arrived on June 16, two on June 17, and three on June 18. Of those that stay in the islands at the end of their day, all were scheduled to fly back on June 20 with one exception.

N8790Q looks to be an operational spare that sits in Honolulu. It was pressed into service on the 19th, but it hadnʻt flown before that since June 16. Iʻm not sure how long the airplane stays in Honolulu, but it will rotate back into the mainland once its tour of duty as a spare is over. Another aircraft will take its place.

This kind of flying is good for these airplanes, especially for the engines on these B737 MAXs which need more time between flights than any older engine. Putting them on a mix of long and short flights means that the cycle counts donʻt climb too high, and they donʻt face that same operational stress that dedicated interisland aircraft deal with for lengthy periods of time.

Could Hawaiian be interested in this model? Itʻs entirely possible, as I suggested yesterday. After all, on June 19, Alaska already had many B737s flying into the islands.

• B737-800: SAN-OGG, SEA-LIH, SFO-KOA
• B737-8 MAX: BUR-HNL, PDX-LIH, SAN-LIH, SEA-LIH, SFO-LIH, SLC-HNL
• B737-900ER: SEA-KOA
• B737-9 MAX: ANC-HNL, LAX-HNL, ONT-HNL, PDX-OGG/KOA, SAN-HNL/KOA/OGG, SEA-OGG/HNL/KOA, SJC-KOA

Some of these routes have operational issues with shorter runways, like Burbank and Līhuʻe. Other markets just arenʻt all that big, like Salt Lake to Honolulu. And remember, this is summer. In winter when demand is lower, a smaller B737 starts to look more attractive for the income statement on more routes.

This seems like a good way to run your fleet, but only if you donʻt need a different interior configuration — as talked about yesterday — and youʻre okay with the additional maintenance headaches that come with older aircraft. Were it not for those, Iʻd say this would be an easy decision to emulate Southwest. But there are a lot of ways to skin this cat, and Hawaiian management is going to have to evaluate them all before making a final decision.