BAO's Flight Simulator Flight Shop (FSFS) is a great add-on for Microsoft's Flight Simulator 5.1 that not only 'fixes' many bugs and incomplete features in the original release (such as blocky coastlines and ATC features), but allows you to create custom planes for use in the program.If you have both FS5.1 and FS98 installed, you can download the FS98 converter file from this website to have the planes you create in FSFS work in FS98 version. The program is quite complicated, but your effort to navigate the steep learning curve will be rewarded with a powerful and versatile application that can bring just about any flying object in your fantasy to reality in FS5.1. If you are not interested in designing planes but enjoy FS5.1, you can still enjoy the many bugfixes and additional features (including better-looking buildings and more airports) that this add-on includes. All in all, a great add-on to a great program that was worth the money when it came out, and remains very useful to this day; you can still find plenty of fanmade planes on the Internet that were designed with this underdog.