Yeti sports 4. The sixth best thing about sims like FSX is that they tend to be fully customisable through third-party add-ons. In essence, when you load up something like, you’re effectively starting a flight OS into which you can install whatever program you see fit to make your time in the sky more rewarding. The only problem is that there’s so much out there in the way of custom planes, landscapes, editors and so on, that newcomers can be so stymied by choice that the usual response is to collapse into a foetal position and weep for a week before opting to stick with the vanilla program.