You will probably remember the issues I've had with the FO changing MCP values whilst I'm flying online, despite the mute symbol being illuminated. I had this problem a while back with the 737PIC version, but have also had it to a much lesser extent with the 767 as well. I think it occurs less with the 767 due to you changing the commands from "heading xxx" to "SET heading xxx". Either way this solution works for me in both aircraft.Anyway I've finally figured out the exact set of circumstances which result in the FO misbehaving. Let me explain....Try setting a flight up and whilst pressing the mute button, give a command, then IMMEDIATELY release the mute button as soon as you stop speaking. When I do this the FO will act on the instruction 100% of the time. Now do the same again, but this time continue to hold the mute button down for around one second after you have finished speaking the command. Now the FO never acts on the command, just as he's supposed to. I've been playing around today and can produce these results in every circumstance.Now that I know what the score is, I can easily work around it simply by remembering to hold the button down for a second after speaking, however it's a bit unnatural and could possibly lead to problems at times when ATC is busy. With your knowledge of the workings of the program, it would be great if there was a really easy way for you to make the mute function continue for that tiny bit longer after the button is released.Hopefully you will be able to reproduce this yourself as I've tested it on various joysticks, wired/wireless keyboards ect and as it's the same every time, it shouldn't be something related to my particular hardware/software ect. FS2004 only.

Hi,Glad you figured it out. You really had me scratching my head there.I haven't personally experienced what you mentioned, but I'll look into the adding the extra 1 second delay when you release the mute key.Cheers,