I hope someone from Captain Sim can help answer my question. If it's any help, I have the base 757-200, and the expansion model 757-300, version 4.6. I know back in the days of FS9, the transponder worked just fine, but I'm talking almost 10 years ago. I know many folks have moved on to QualityWings, but I've stood with Captain Sim's model because the aircraft has a more rustic and real look to it than QualityWings. Just give me my transponder!