arefixz said everything, I just want to insist on :
(.../...) Be warn that GW is not easy as BW, (.../...)
GWs are difficult, or very difficult. In current GW3, 40% of companies starting day one did not survive one year, and after 27 months of gameplay, the churn rate is already at 56%, and plenty of companies are surviving now because they hedged cleverly but will die when their hedge will finish, or are too weak to survive the upcoming events (2001 was not the best year for air transport, by far).
Previous GW3, I HQ'd in CDG. Had 5 opponent from start, 4 next game year, and 7 or 8 arrived later, either through HQ'ing or basing here. Exactly one based guy(a top 10 player) survived there up the end of the game, not leaving me alone. GWs are difficult.
All the art is to grow fast enough to take the market, but not too fast to avoid being excessively vulnerable. If you are too small, the big boys in your airport will prevent you from breathing, just by existing and taking all the place. If your market is mature and you are leasing 100% of your airframes, your profit will dive enough to kill you.
The second difficult part is to prepare transitions. An airframe lasts 24 years, less if it's soviet steel. The shortest GW lasts 38 years. You need to manage fleet renewals to survive. It's long, tedious, and full of traps. It needs to be forecasted years, if not decades, in advance. It's usually where "good" players discover they are not good enough, despite being far better than average.