i did a flight from cyul to kstl..i programed a direct route with no waypoints..the magenta line was from airport to airport.at cruising altitude i engaged the nav switch to keep me on course automatically...about a third into the flight...a chime sounded...the magenta line dissapeared and the nav light went out..i did the same flight again and the same thing happened at the same spot..what in the world caused this?

Interesting. In one of my flights, I had the whole flight plan disappear from the ND, but the FMC was fine. After a few minutes, it re-appeared. But never seen what you are saying ...- Neeraj.