Perhaps this is what you mean by obvious, but at some points in a gameworld there are no used a/c of the type you want. Another reason to consider new, is your long term vs short term planning. You can plan a steady stream of aircraft of the same type and not sit on the used market, hoping you'll get the a/c you want. When you start up it may well make sense to buy used because you get them practically immediately, but it is erroneous to think you are always getting a good financial deal. Other than the delivery cost, new a/c generally cost you less than used because you get new at market value or less (the more you order at once, the bigger the discounts), whereas used always have a mark-up for the seller, and used aircraft are going to cost you more in maintenance costs over the long term because of the wear and tear already on them. Maintenance costs increase with age, so the saving you get on buying an older plane is offset by those costs over time. Lastly, you can configure new aircraft anyway you want without extra expense, unlike used aircraft which will cost you extra to configure them to fit you needs.