Not such a silly question if you substitute the aircraft carrier scenario for say a boat in distress (or search & rescue) with a known position and a course and speed(or known/predicted drift rate).
I would work this out by taking known position extrapolating this with course and speed (eg. 30kts @ 2hours + 60nm) to calculate position at ETA and apply pnr to this position. Of course the ETA would need to be adjusted according to targets course relative to you.
BTW some Universal FMCs have a drifting target function which will do this for you.
Even two hours drift or movement at say 15kts equates to 30nm and in low vis at low level this can make a difference.
Last edited by Bozzo; 11th April 2008 at 05:37.