A system of preferred IFR routes helps pilots, flight crews, and dispatchers plan a route of flight to minimize route changes, and to aid in the efficient, orderly management of air traffic using Federal airways. Preferred IFR routes are designed to serve the needs of airspace users and to provide for a systematic flow of air traffic in the major terminal and en route flight environments. Cooperation by all pilots in filing preferred routes results in fewer air traffic delays and better efficiency for departure, en route, and arrival air traffic service. [Figure 3-3]

Preferred IFR routes are published in the Airport/Facility Directory for the low and high altitude stratum. If they begin or end with an airway number, it indicates that the airway essentially overlies the airport and flights normally are cleared directly on the airway. Preferred IFR routes beginning or ending with a fix indicate that pilots may be routed to or from these fixes via a standard instrument departure (SID) route, radar vectors, or a standard terminal arrival route (STAR). Routes for major terminals are listed alphabetically under the name of the departure airport. Where several airports are in proximity they are listed under the principal airport and categorized as a metropolitan area; e.g., New York Metro Area. One way preferred IFR routes are listed numerically showing the segment fixes and the direction and times effective. Where more than one route is listed, the routes have equal priority for use. Official location identifiers are used in the route description for very high frequency omnidirectional ranges (VORs) and very high frequency omnidirectional ranges/tactical air navigation (VORTACs), and intersection names are spelled out. The route is direct where two NAVAIDs, an intersection and a NAVAID, a NAVAID and a NAVAID radial and distance point, or any navigable combination of these route descriptions follow in succession.


Air route traffic control centers are responsible for specifying essential substitute airway and route segments and fixes for use during VOR/VORTAC shutdowns. Scheduled shutdowns of navigational facilities require planning and coordination to ensure an uninterrupted flow of air traffic. A schedule of proposed facility shutdowns within the region is maintained and forwarded as far in advance as possible to enable the substitute routes to be published. Substitute routes are normally based on VOR/VORTAC facilities established and published for use in the appropriate altitude strata. In the case of substitute routes in the upper airspace stratum, it may be necessary to establish routes by reference to VOR/VORTAC facilities used in the low altitude system. Nondirectional radio beacon (NDB) facilities may only be used where VOR/VORTAC coverage is inadequate and ATC requirements necessitate use of such NAVAIDs. Where operational necessity dictates, navigational aids may be used beyond their standard service volume (SSV) limits, provided that the routes can be given adequate frequency pro- Figure 3-3. Preferred IFR Routes. tection.
The centerline of substitute routes must be contained within controlled airspace, although substitute routes for off-airway routes may not be in controlled airspace. Substitute routes are flight inspected to verify clearance of controlling obstacles and to check for satisfactory facility performance. To provide pilots with necessary lead time, the substitute routes are submitted in advance of the en route chart effective date. If the lead time cannot be provided, the shutdown may be delayed or a special graphic NOTAM may be considered. Normally, shutdown of facilities scheduled for 28 days (half the life of the en route chart) or less will not be charted. The format for describing substitute routes is from navigational fix to navigational fix. A minimum en route altitude (MEA) and a maximum authorized altitude (MAA) is provided for each route segment. Temporary reporting points may be substituted for the out-of-service facility and only those other reporting points that are essential for air traffic control. Normally, temporary reporting points over intersections are not necessary where Center radar coverage exists. A minimum reception altitude (MRA) is established for each temporary reporting point.