One more question;
Is it smart to open up a new base for my airline yet, or should i wait?
I disagree with minerva on this one personally. I think the option of opening a new base is quick viable for you, though it may not be the option that best suits YOU as the player. Please read further.
Firstly, I must digress from the overall topic for a brief moment. You only have 5 fleets in operation, due to your order of B737NG, not seven as stated earlier. Each of these fleets, with the exception of one or two fleets have a decent amount of aircraft in each, thus warranting their existence. However, I do believe your lease of the A300 and the associated addition of another fleet was a mistake, but this is not my point. Back on topic.
At this point in the game, many large airports are actually not full. Though five plus airlines are based there, these airlines do not have that many aircraft as they are still waiting for their new shipment from the factory. And because these airlines do not have many aircraft yet, (though they are beginning to receive them so this won't last much longer) many routes AND slots are left open. If you can establish a profitable base using used market aircraft (or readably available new aircraft) now, I believe it will give you an advantage over these same players later on in the game. On the this same point, because these airlines are in gridlock over aircraft, it severely limits the quality and amplitude of their base defense.
Secondly, several fleet types, including the RJ100 which you currently operate, are very easy to acquire quickly new. If you can manage to save 15 Million, take a four or five year loan from the bank for your maximum (most likely 50+ Million at this point), I believe you could open a base at a medium to large airport and still have enough money left over for spending money. With the longer term loan, you will spend less per week on loan fees, improving your cash flow. Though your cash flow will be slightly less (say 200,000 less than current), you will have multiple aircraft on order, allowing you to focus on expansion of your route networks. As you are focused on your route expansion, you can devote your income to finding suitable aircraft, in fleets that you already operate, from the used market place and in turn lease them.
I am not sure the best location to place a base, as I have stopped looking for a while now, but be sure you have a large amount of moderate to high demand routes, there are plenty of slots, and that your competition won't have a significant amount of aircraft arriving for some time. I would also only recommend operating the new base no more than 2 fleet types that you currently operate. This would extend the 15% increase in commonality expenses ONLY to those two fleet types, minimizing your increased weekly costs. (The fixed, start up fee is obviously a one time expense.)
Now, I also must warn you that because many of these airlines have large amounts of aircraft arriving in the next few years, they will begin to open other bases. San Diego has historically been a popular base for multiple airlines, and because there are only 2 airlines currently based there, I suspect a few will begin to want to open operations there. To help discourage this from happening, you should have a LARGE percentage of the routes already taken, attempting to make some place else more desirable. However, once others begin opening at these more desirable locations, San Diego will become more relatively attractive. The simple fact remains, that it is cheaper and more conservative to continue expanding aggressively from San Diego to help minimize the likelihood of another airline opening a base.
One last point, before you open a base, make sure you have at least 5 aircraft sitting on the ground idle and many more ordered and arriving soon. This will allow you to establish a firm foothold quickly, potentially surprising the current residents. The minimum amount of aircraft need to open a base is three.The underlining fact to remember is that opening a new base is risky. You can win big or lose big with each base you open.