Updates For Gulfstream G500; G600 Programs Every now and then we at JF alert you to the progress of most in-development programs and the G500 and G600 test programs are no different. Since the last update these programs have continued to mature. At this point up until a few days ago, the Gulfstream G500 program amassed 3,460 flight hours or equal to around 905 flights. Since the G500 program was online before the G600 this particular program is much further along as expected. The G500 testing regime has five aircraft involved while the G600 has four to date.