b.
HIGH ALTITUDE AREA - The airspace above FL450 where no predetermined routes exist and free selection of routes is permitted.

(1)
From above FL450 to FL600 navigation may be conducted via the NAVAIDS serving the jet route system provided the NAVAIDS selected to define a route are not more than 200 NM apart.

(2)
The route of flight above FL600 will contain at least one fix within each ARTCC area through which flight is planned without regard to distance between fixes. These fixes designated will be in relation to NAVAIDS serving the jet route system. Position reports and estimates may be requested in the event radar monitoring is not possible and a crossing of courses will occur. Fixes used are not compulsory reporting points. Military organizations using the airspace above FL600 will employ coded altitudes in position reporting. These codes are changed annually and are available from HQ ACC/DOR, Langley AFB (KLFI), VA, DSN 574-7982.

c.
JET ROUTE SYSTEM - Specified routes established in the airspace from 18,000’ MSL to FL450 inclusive.

(1)
Jet routes are identified by "J" followed by the route number, e.g., J151. Jet routes are predicated solely on VOR or VORTAC navaids except in Alaska where some jet route segments are based on LF/MF navaids.

(2) Reporting points are designated for jet routes. Aircraft will report over these points unless otherwise advised by ATC.
(SPEC/ENR 3.5-2)

d. AREA NAVIGATION (RNAV) ROUTES
(1) Published RNAV routes, including Q-Routes and T-Routes, can be flight planned for use by aircraft with RNAV capability, subject to any limitations or requirements noted on enroute charts, in applicable Advisory Circulars, or by NOTAM. RNAV routes are depicted in blue on aeronautical charts and are identified by the letter “Q” or “T” followed by the airway number (e.g., Q13, T205). Published RNAV routes are RNAV-2 except when specifically charted as RNAV-1. These routes require system performance currently met by GPS or DME/DME/IRU RNAV systems that satisfy the criteria discussed in AC 90-100A,
U.S. Terminal and En Route Area Navigation (RNAV) Operations.
(2)
 Q-routes are available for use by RNAV equipped aircraft between 18,000 feet MSL and FL450 inclusive. Q-routes are depicted on Enroute High Altitude Charts.

(3)
T-routes are available for use by RNAV equipped aircraft from 1200 feet above the surface (or in some instances higher) up to but not including 18,000 feet MSL. T-routes are depicted on Enroute Low Altitude Charts.

(4)
Unpublished RNAV routes are direct routes, based on area navigation capability, between waypoints defined in terms of latitude/longitude coordinates, degree-distance fixes, or offsets from established routes/airways at a specified distance and direction. Radar monitoring by ATC is required on all unpublished RNAV routes.

(SPEC/ENR 3.3-1)