Hi, I might not be able to give advice from many years of experience but I do have some experience and a good knowledge of the economical backings of the game. The route that many of those people with 100 new planes is very risky because they can suddenly find themselves facing overexpansion and the rapid spike in fuel prices and find themselves in an uncomfortable position. Most of their planes are leased new, which means they must keep them a minimum of 1 year if they chose a 5 year lease, from where they must further pay 50% of the remaining lease. Sometimes it pays off tremendously, but until about the 5th year you can't really know. I myself am not one to try too much risk, but I do like expansion with a reasonable amount of growth, slower than these other methods but much more stable and safe financially. Most of the newer models won't be around until about the 3rd or 4th year on the used market, as this is when many airlines begin to drop out from disinterest or other reasons. I would definitely advise keeping one fleet or two fleets max, having one fleet of the large 100+ seat aircraft, and another with the smaller capacity, around 75. This will do much more to increase your CI as well, which will give you an advantage over competition. It doesnt have to be new to be economically efficient, try to start with the older planes and slowly invest in the newer fleets. For example, I am flying 727s as my main fleet, I have 5 of them with an average age of around 17 or 18 years, I have just started two more fleets with brand new planes, the 737-300 and MD-90, however, I must admit that I will need to get rid of the MD-90 fleet more than likely for economic reasons. Be sure to always have some form of advertising going on and have good route images, growth will be slow at first so be sure to have some extra money around in case your routes are unprofitable in the beginning. I hope this might help, you can reply on this or send a message if you wish to discuss tactics or anything.