For GutShot:
A. FAA's Interpretation of FAR 121.471
Because the Whitlow Letter7 constitutes the FAA's inter-
pretation of its own regulation, that interpretation must be
afforded substantial deference and upheld unless "plainly
erroneous or inconsistent with the regulation." Thomas Jef-
ferson Univ. v. Shalala, 512 U.S. 504, 512 (1994); see also
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5 If the flight is away from the gate but not yet in the air, the
flight may not take off. As a matter of enforcement policy, the
FAA will not charge a violation of the rest requirements if a delay
that first becomes known after the flight is in the air disrupts the
scheduled flight time, provided the required minimum reduced rest
and the compensatory rest occur at the completion of that flight
segment. See Whitlow Letter at 4.
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The FAA responds that the phrase "scheduled completion
of any flight segment" can reasonably be understood to
include a re-scheduled flight time based on actual flight
conditions. To be sure, "scheduled completion" can be con-
strued narrowly to refer only to the originally scheduled
flight completion time. The point, however, is that the FAA's
more expansive interpretation is not unreasonable. A re-
scheduled completion of a flight segment based on flight
conditions existing in fact is nonetheless a "scheduled" com-
pletion. Nothing in the text of FAR 121.471 or in the
ordinary usage of the word "scheduled"8 dictates that the
timetable of a particular flight segment can be determined
only when the schedule is originally created regardless of
adjustments made necessary by then-current conditions.
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1 The flight time limitation rules applicable to "major scheduled
air carriers" and "other airlines operating large transport category
airplanes" are contained in Part 121 of the FAR. The flight time
limitation rules applicable to scheduled air carriers operating air-
planes of 30 or fewer seats and air taxi operations are contained in
Part 135 of the FAR. The substance of the rules in Parts 121 and
135 is essentially the same and the rules are likewise interpreted.