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.