Originally Posted by West Coast
"You do not use "Heavy" in the enroute phase of flight"
Reference please.
The current US AIP, page GEN 1.7-12:
In the U.S., the word “heavy” is used in all communications with or about heavy jet aircraft in the terminal environment. In the en route environment, “heavy” is used in all communications with or about heavy jet aircraft with a terminal facility, when the en route center is providing approach control service, when the separation from a following aircraft may become less than five miles by approved procedure, and when issuing traffic advisories.
Of course we yanks love to contradict ourselves, AIP again:
29.8.4 For operations conducted behind heavy
aircraft, ATC will specify the word “heavy” when this
information is known. Pilots of heavy aircraft should
always use the word “heavy” in radio communications.