boondoh, yes, aircraft are rarely restricted to a specific route.

The same aircraft can turn up all other the place - literally. I was once sitting at HKG waiting to board the CX 888 to YVR and then JFK, when I saw a BA744 taxiing out and noted its registration.

When I eventually arrived at JFK some twenty hours later I saw the very same BA 744 which must have flown HKG-LHR-JFK - i.e. the other way around the world to reach the same destination.