Did you only increase frequency when the planes were full to a "green" level? I ask because in my examples secondary airport 1 is in the 90-100% seat fill range on an ATR72, which I'm slowly increasing flights from, while secondary airport 2 is in the 50-65% range on an ATR72. I have an ATR42 which I'm using for the smaller airports, but I don't want to try and use it on the secondary airport 2 as it's definitely large enough to fill several larger planes and if I start to take any market share then the ATR42 will be too small.
It really depends on the individual market-conditions. A number of flights are not green but they get green as soon as I offer enough connecting-flights between my hubs. Regarding Sparrow Air, I´ve decided to offer a vast amount of frequencies between my domestic hubs to increase the chances that the feeder-effect starts to kick-in.
The hubs also allow me to provide routes to secondary destinations with healthy loads and I also tend to think “mid-term”. Five flights a day with a 137-seat MD-80 might be too much at the beginning but adequate in the mid-term and I don´t need to monitor a growth on that particular route. Scheduling a cheap MD-80 to offer five short haul flights is functioning for me.
Another approach is needed for difficult markets. Flights to China from Indonesia are not automatically well-booked. Important ILs are needed and I tend to begin with two to three flights a week and gradually increase the frequencies as soon as I see enough demand to increase the number of flights.
Additionally there are regional-subsidiaries which feed my hubs and which also assist me to fill mainline aircraft. I also rely heavily on important ILs.
The demand on domestic trunk routes is that high that I could instantly offer 50 additional daily flights but slots are rare and it is getting difficult to grow at Jakarta on devau (due to my networks) but hey: I respond to demand and I need to have a strong network to compete against much bigger airlines in the region.
It is (IMO) also an important factor to “know” the market in AS. I think that I learned a little bit of the Indonesian market and I know that some routes would work while others won´t be viable.
I once wrote that I don´t like the 100%-green load factors on many flights between major hubs of mine because I don´t know how many passengers were left behind! In real world, an airline knows that and can adjust capacities and fares to reflect the demand and to make full use of the demand. Many airlines also “control” demand through fares etc…
Last but not least I started my current Sparrow Air with 7 million and established a regional subsidiary with 3 million. The subsidiary allows me to use smaller aircraft which are not welcomed at my mainline. I wanted to avoid the situation to start with ATRs and to experience that the ATRs are far too small. ATRs are nice for feeder services.
In short: Try to establish an airline with some major trunk routes which allow your airline to generate enough income. I think that it´s very important to have routes which “always generate money”. Add secondary destinations and these flights will feed your other flights vice versa.
Think forward and not only until tomorrow.