*Hits you hard with the diminishing returns stick*
Im sure this guy already gets the point, but that wont stop me from ranting.
High frequencies = Bad (in almost all cases)
The reason your not making much on a route with a frequency of 6 is due to an economic principal called 'Diminishing Returns'
Here is a defininition taken from a website
Diminishing returns
The more you have, the smaller is the extra benefit you get from having even more; also known as diseconomies of scale (see ECONOMIES OF SCALE). For instance, when workers have a lot of CAPITAL giving them a little more may not increase their PRODUCTIVITY anywhere near as much as would giving the same amount to workers who currently have little or no capital. This underpins the CATCH-UP EFFECT, whereby there is (supposedly) convergence between the rates of GROWTH of DEVELOPING COUNTRIES and developed ones. In the NEW ECONOMY, some economists argue, capital may not suffer from diminishing returns, or at least the amount of diminishing will be much smaller. There may even be ever increasing returns.
http://www.economist.com/research/Economics/searchActionTerms.cfm?query=diminishing+returnsThere are other terms involved such as benefit and satisfaction. The satisfaction you recive for each additional unit, is incrementaly less than the previous. Here are some examples.
You go to a restaurant and order a piece of pie, that pie is great, its the best pie in the world. You tell the waitress, keep em coming, this pie is awsome! Second piece comes around, its also good, but somehow not as good as the first, since your already used to the flavor. Third piece is even less good, your stating to get full and you dont really want anymore. Forth piece downright bad, all you can do is sit there and poke at it. Its the same pie as before, but it satisfies you less because youve had enough.
Lets look at the practive. Diminishing returns plays many rolls in AM, alot of the mathematics are defined by this.
The most money you can extort from your passengers is by operating an aircraft with .5 frequency. That means price per seat, not total income. So say the income you make from a .5 flight is X. You can run a higher frequenys, such as 1, but the income will not be 2X. it will be more like X+1/2X. Additional frequencies will look like X+1/2X+1/3X etc. Each additional frequencz will be worth less than the previous.
It can even get to the point where the opperations costs of the aircraft begin to detract from the finnal income. You might even be able to make more total income opperating a craft at a frequency of 2, than you would be at a frequency of 4.
All your doing through adding multiple frequencys is adding more seats into the route. Again through diminishing returns theory, the more seats there are, the lower thier value. It also helps to look at a competition, there might be 10 players running routes ONT/LAX, there are already plenty seats on this route, so you know you cant charge that much for new ones. Atleast not as much as on a route where there are fewer seats in existance.
You might argue ''But real airlines do it, why cant I'' Well Johnny, this isnt real life. This is a computerized simulation based upon mathematic equasions, simulation does not need to mean realism. The mathematics that runs this game is lined out based upon critera, there is no human element. No little suzie that is visiting her grandma in phoenix, No aunt Beru flying to her nephews graduation at the starfleet acadamy.
So all this being said, i would not recommend putting a craft on a frequency higher than 1. Out of all 500 plus flights i have, maybe 3 are above 1, and thats only to spite competators. So use your hardware well, spread it out, and look for routes with the lowest number of seats on them, with the highest number of potential passengers.