Hi Mark.Thanks for your reply.

One other thing to ask your expertise.I use a commercial route planner which exports to different formats including FSX's native .pln,which when I select AP,and NAV,the 707 uses to track that flightplan.

However,as this commercial flight planner allows me to add SIDs and STARs,as I near my arrival airport I add those additional waypoints to that flightplan,then update it in FSX,when I select NAV again,the aircraft does an about turn and is heading backwards along that flightplan.How can I get it to now track the new updated flightplan? Instead,I have to use HDG and track the route manually.