ant1
What about FAR 91.181?
Sec. 91.181
Course to be flown.
Unless otherwise authorized by ATC, no person may operate an aircraft within controlled airspace under IFR except as follows:
(a) On a Federal airway, 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.
That regulation was written long before GPS. If either aircraft in the Brazil midair had used 1 mile right both would have passed in the night, neither knowing how close they came. Any pilot not using an off set in certain areas of the world are either negligent or ignorant or both.