The ATS route designator
shall consist of a basic designator comprising a letter and a number
Basic Route Designators
comprise a letter and a number.
The designator may be
supplemented if necessary by:
a) One prefix:
1) K to indicate a low
level route primarily for helicopters
2) U to indicate that the
route, or part of it, is in upper airspace.
3) S to indicate a route
established exclusively for use by supersonic aircraft.
b) One additional letter
to indicate the type of service provided or the turn performance required on
the route.