Generally, it depends how you play your cards. There are different variables, one is where you base, if you base in a larger airport, you'll be more likely to have a higher DOP, which in turn, makes it easier to afford planes (note that this is true only for hte beginning of the round, later on I hear it gets very hard.) Other variables are aircraft choice, competitors (who, how many, how large). If you want to avoid competition more, try to base from airports that are smaller in size, like Krakow, Gdansk, Katowice. If you really want to reduce competition to as close to zero, try to base in a city with a pax number of less than one million (should tell you, at that point, it is not advisable to lease aircraft, as they might not make you desired MOP (Monthly operating profit) as they have that 5% rule (was it 5%?) for leasing .
I'll tell you some of my experiances from before, preferably the early 1950s and early 1970s round before multiworlds was implemented.
On both, I typically started out in RZE (Rzeszow), which has a pax number of some 190K. It starts VERY slow for you like this, and your DOP will typically be below 100K. You'll also have to plan carefully and not buy anything with less than 20 seats for your "2nd" plane, as they'll have a harder time of rolling in a profit. When you get some more of that type (like 4 to 5), look into purchasing your first 50 seater (by then a game year might've passed). After that, it should be much smoother sailing for you at that point. After some time, and establishing close to 50-75 routes, I went ahead and opened up a new base at another small airport (In the 1950s, it was Kaliningrad, in the 70s it was Kharkiv (I remember adding that one into, I think it was one of the first ones I did)). Then I started to look at larger bases with pax numbers with larger than 1 mil pax.
In the 1950s round I got up to being 200th out of some 2000 players, and in the 1970s I ended up being like 150th out of a simiar (or larger) amount. If those rounds were allowed to continue as planned, I think I could've been pretty close if not in the top 100 players.
The other rule of thumb is cover EVERYTHING you can that will bring in a good reasonable profit, specifically stuff that is closer togeather. As that is where easier money should be (does not apply well for the LHRs, CDGs, and ORDs of the world I have heard, as they get crowded quick).
