hmm... so what you are saying is to protect the players who dump on routes from going negative? or that there should be a minimum ticket price where everyone is going to be at?
either ways, this would not work.
Nope, not what I meant... Let me try to explain it (bare with me).
You already have something in place that tells us what the cost of running a route are. These are purely made up numbers but lets say I set up a route from JFK-LAX; as I price my route it already tells me what the costs of running that route are which are then subtracted out of the profit to give me my profit for that route. 100,000 base earnings, 12,000 costs, 88,000 profit.
If I use a larger plane my base earnings might be 125,000. The costs for a larger plane seem to be higher though so let's say this plane has 18,000 in costs for a total profit of 107,000.
You already scripted in what the costs are for each plane for each route, so you've already done all the hard work.
My suggestion is to basically set it so that you can not create a route that will make you earn a negative profit on PURPOSE.
Essentially have it scan of a minus symbol then give you an error like when you try to sell a plane for too little too much. "I'm sorry, but you have priced yourself to not earn a profit for this route. Try again and make sure you have positive earnings."
How this would apply to the game is that (using the above references) airline #2 with the larger plane could only drop their fare to the point where their base earnings are 12,000 euro (minus 12,000 in route costs = 0 euro profit). That fare threshold might be 15 euro. The first airline using the smaller plane with LESS calculated route costs might have a fare threshold of 8 euro. Thus they could technically price themselves at 14 euro and still make a profit.