Ian,
Now I see that others have found that the “Nav Data Out of Date” message appears only with the Zibo mod B737-800X, which is the aircraft I have been flying for the past two years in XP. By far this is the best airliner model I have found, and I really enjoy using it. Even with all Navigraph files downloaded and installed correctly, per Support instructions on this Group, the 737 Zibo continues to correctly show the cycle as 2103, but the valid dates listed adjacent on the FMC are still shown as Feb thru Mar, not Mar thru Apr 22 as it should be. So is this a Navigraph problem, or is it a strictly an XP11 .53 problem? Seems like this has been a problem for a while now.