Section 3. Federal Airways

1. DEFINITION

1. Federal airways consist of VOR Federal airways and Low/Medium Frequency (L/MF) (Colored) Federal airways.
2. Unless otherwise specified, the names appearing in VOR Federal airway descriptions are the names of VOR or VORTAC navigation aids. DME fixes and latitude/longitude coordinates are not used in Federal airway descriptions.

1. NAVAID SPACING

1. VOR Federal airways are based on VOR or VORTAC NAVAIDs which normally are spaced no farther apart than 80 NM. They may be based on more widely spaced NAVAIDs if a usable signal can be provided and frequency protection afforded for the distance required (see FAA Order 9840.1, U.S. National Aviation Handbook, for the VOR/DME/TACAN Systems).
2. L/MF (Colored) Federal airways are based on Non-Directional Beacon (NDB) NAVAIDs. NDB NAVAID spacing is determined on an individual basis.

1. VERTICAL AND LATERAL EXTENT

The standard vertical and lateral extent of Federal airways is specified in FAA Orders 8260.3, United States Standard for Terminal Instrument Procedures (TERPS), and 8260.19, Flight Procedures and Airspace. Nonstandard dimensions may be specified, when required, subject to any flight inspection limitations and by paragraph 20-1-6, Base Altitudes, of this order.

1. Each Federal airway is based on a center line that extends from one navigational aid or intersection to another navigational aid (or through several navigational aids or intersections) specified for that airway.
2. Unless otherwise specified:

1. Each Federal airway includes the airspace within parallel boundary lines 4 miles on each side of the center line. Where an airway changes direction, it includes that airspace enclosed by extending the boundary lines of the airway segments until they meet.
2. Where the changeover point for an airway segment is more than 51 miles from either of the navigational aids defining that segment, and—

1. The changeover point is midway between the navigational aids. The airway includes the airspace between lines diverging at angles of 4.5° from the center line at each navigational aid and extending until they intersect opposite the changeover point; or
2. The changeover point is not midway between the navigational aids. The airway includes the airspace between lines diverging at angles of 4.5° from the center line at the navigational aid more distant from the changeover point, and extending until they intersect with the bisector of the angle of the center lines at the changeover point; and between lines connecting these points of intersection and the navigational aid nearer to the changeover point.

1. Where an airway terminates at a point or intersection more than 51 miles from the closest associated navigational aid, it includes the additional airspace within lines diverging at angles of 4.5° from the center line extending from the associated navigational aid to a line perpendicular to the center line at the termination point.
2. Where an airway terminates, it includes the airspace within a circle centered at the specified navigational aid or intersection having a diameter equal to the airway width at that point. However, an airway does not extend into an oceanic control area.

1. Unless otherwise specified—

1. Each Federal airway includes that airspace extending upward from 1,200 feet above the surface of the earth (or higher) to, but not including, 18,000 feet MSL, except that Federal airways for Hawaii have no upper limits. Variations of the lower limits of an airway are expressed in digits representing hundreds of feet above the surface or MSL and, unless otherwise specified, apply to the segment of an airway between adjoining navigational aids or intersections; and
2. The airspace of a Federal airway, within the lateral limits of a Class E airspace area with a lower floor, has a floor coincident with the floor of that area.

1. A Federal airway does not include the airspace of a prohibited area.

1. WIDTH REDUCTIONS

1. Width reductions are not applicable to L/MF (Colored) Federal airways.
2. For ATS routes other than L/MF (Colored) Federal airways, a reduced airway width of 3 NM on one or both sides of the centerline may be established from the NAVAID to the point where 4.5 degree intersecting lines equal 3 NM. Normally, lines perpendicular to the airway centerline determine the ends of the reduced portion. If required, the ends of the reduced portion may be defined differently. A reduced width is permissible to obtain additional traffic capacity and flexibility through the use of multiple routes and to avoid encroachment on special use airspace or other essential maneuvering areas. Width reductions are considered the exception rather than the rule and are approved only where adequate air navigation guidance and justification exist.