Regulation Text
Unless otherwise authorized by ATC, no person may operate an aircraft within controlled airspace under IFR except as follows:
(a) On an ATS route, along the centerline of that airway.
(b) On any other route, along the direct course between the navigational aids or fixes defining that route. However, this section does not prohibit maneuvering the aircraft to pass well clear of other air traffic or the maneuvering of the aircraft in VFR conditions to clear the intended flight path both before and during climb or descent.
[Docket 18334, 54 FR 34294, Aug. 18, 1989, as amended by Amdt. 91-296, 72 FR 31679, June 7, 2007]
Research Notes
Section 91.181 — Course to be flown — requires pilots operating IFR to fly the centerline of the airway, route, or course (except for off-route deviations specifically authorized by ATC).
Paragraph (a) — On a Federal airway: The pilot must fly along the centerline of the airway.
Paragraph (b) — On any other route: The pilot must fly along the direct course between fixes, unless deviation is required by weather, terrain, or other safety considerations.
Operational reality: Modern IFR navigation is GPS-based and pilots fly direct courses defined by lat/long coordinates. The reg captures the basic obligation: stay on the published or assigned course. Deviations (for weather, ride, etc.) require ATC clearance.
Off-route operations: When ATC clears an aircraft on a 'direct ABC' or 'direct present position to XYZ,' the pilot flies the great-circle course between those points. The pilot must respect MEAs or minimum off-route altitudes per § 91.177.
Reference: FAA-H-8083-16 Chapter 3.
Amendment History
Amendment History Coming Soon
Every time this regulation changes, we'll record it here — the date, what was amended, and a plain-English summary of what shifted.