February 23, 2006

Patrick M. Ryan

Aviation Safety Inspector

FAA Detroit FSDO-23

Willow Run Airport-East Side

8800 Beck Rd.

Belleville, MI 48111

Dear Mr. Ryan:

This letter responds to your May 12, 2005 request for an interpretation
of 14 C.F.R. section 121.503(a) (subpart S).

**SCENARIO AND QUESTION PRESENTED**

The scenario you present involves a 2-pilot crew, scheduled for a 3-leg
as follows: outcome:

> **[Scheduled]{.underline} [Actual]{.underline}**

**Legs 1 & 2**: 3.5 hours 4.5 hours

**Leg 3**: 4 hours 4 hours

**Total**: 7.5 hours 8.5 hours

You state that "the crew and company know what is scheduled and what is
likely to be actual." In addition, the crew and company also know that
the actual times will exceed 8 hours, as per 14 C.F.R. 121.503(a)
without an intervening rest, prior to conducting Leg 3.

Your question is whether the company may dispatch the crew and the crew
launch out on Leg 3 knowing ahead of time that they will exceed 8 hours.
Your view is that the company may not dispatch, nor may the crew take,
Leg 3.

**ANSWER**

We understand your view to be that the crew may not be deemed, by
operation of the "circumstances beyond the control of the certificate
holder" rule, to be scheduled to fly for 8 hours or less in any 24
consecutive hours under section 121.503(a),[^1] because the crew and
company know before taking leg 3 that they will exceed 8 hours of flight
time. Instead, the crew is in effect scheduled under section 121.505
(a),[^2] applicable to a crew scheduled to fly more than 8 hours in any
24 consecutive hours, and would be operating in violation of that
section which requires an intervening rest period at or before the end
of 8 hours. We address below, the relevant legal and policy issues that
pertain to a resolution of your question.

Subpart S operations are also subject, by interpretation, to the
"circumstances beyond the control of the certificate holder" rule,
stated in section 121.471(g) [^3] of subpart Q that, in certain
situations, excuses a carrier's violation of the section
121.471(a)(4)[^4] scheduled flight time limits. *See* Nov. 8, 1990
Letter to John H. DeWitt, from Donald P. Byrne, Assistant Chief Counsel,
Regulations and Enforcement Division \[1990-33\] (copy enclosed
)(stating that "past Agency interpretations have applied the same
'circumstances beyond the control of the air carrier' rule to flight
time questions concerning flag air carriers and supplemental air
carriers & commercial operators").

Prior interpretations applying section 121.471(g) to the scheduled
flight time limit in section 121.471(a)(4) articulate the safety
rationale that underpins the rule. The Agency has said that flights may
exceed the flight time limits in a narrowly drawn context, namely:

a\. The delay results from circumstances beyond the control of the
carrier; and

> b\. The air carrier's original schedule is realistic.

*See* Feb. 9, 1993 Letter to David S. Parent, from Donald P. Byrne,
Assistant Chief Counsel, Regulations and Enforcement Division \[1993-3\]
(copy enclosed).

a.  [What the Agency considers to be a circumstance]{.underline}

> [beyond the certificate holder's control]{.underline}

The Agency considers delays due to air traffic control (ATC), adverse
weather, or mechanical problems, as the incidents that, in general,
qualify as circumstances beyond the control of the carrier and, in
general, justify the relief afforded by application of the rule. *See
e.g.,* Interpretation No. 1993-3; and Dec. 13, 1993 Letter to David S.
Parent, from Donald P. Byrne, Assistant Chief Counsel, Regulations
Division \[1993-32\] (copy enclosed). In other words, the Agency
believes that the conditions that fall within the scope of the exception
from the prohibition against scheduling flight time in excess of flight
time limitations should be truly unforeseeable or outside of the
carrier's control. Further, because ATC or weather delays, are sometimes
known in well in advance of the day of a flight's operation, and
mechanical problems may be within a carrier's control, those conditions
do [not automatically]{.underline} trigger an excuse of the carrier's
violation of 121.471(a)(4). Note, in addition, that the conditions are
limited to those that are most important to the safe operation of a
flight sequence.

a.  [What the Agency considers realistic]{.underline}

> [or reasonable scheduling]{.underline}

Over the years, the Agency has issued pronouncements that address
realistic scheduling. *See* Oct. 21, 1958 Letter to J.P. O'Brien from
G.S. Moore, Acting Chief, Air Carrier Safety Division (copy enclosed);
Sept. 17, 1990 Letter to James W. Johnson, from Donald P. Byrne,
Assistant Chief Counsel, Regulations and Enforcement Division,
\[1990-25\] (copy enclosed); and Mar. 20, 1991 Letter to James W.
Johnson, from Donald P. Byrne, Assistant Chief Counsel, Regulations and
Enforcement Division \[1991-8\] (copy enclosed).

Our 1958 letter examined: 1) ALPA's charge that Northwest Airlines
(Northwest) unrealistically scheduled DC-7C aircraft flights on the
Anchorage-Tokyo nonstop westbound route, under the (predecessor) flag
regulations; and 2) Northwest's assertion that "if a pilot is properly
scheduled, he can exceed flight time limitations."

In assessing ALPA's charge of unrealistic scheduling, the Air Carrier
Safety Division of the Civil Aeronautics Administration (CAA), the FAA's
predecessor, reviewed data on the numbers of flights scheduled during
the months of July and August of 1957 and 1958 that exceeded scheduled
flight time. The CAA found that sufficient flights were not conducted in
the 1957 period to make a conclusion on the adequacy of the schedule. As
to the 1958 flights, 11 out of 15 flights met the scheduled flight time
limit in the early part of July 1958, but there was an increase in
flight time in the latter part of July and in August due to far greater
headwind components encountered than those forecasted. Northwest
discontinued the nonstop flight in September of 1958 and instituted a
crew change in Shemya. The CAA concluded that no further action was
contemplated against Northwest.

In response to Northwest's assertion that a pilot who is properly
scheduled may exceed flight time limitations, the CAA said that
exceeding flight time limitations was excused only in certain
situations, namely, because of exigencies beyond the carrier's control,
such as adverse weather conditions. The CAA also stated the standard for
what it did [not]{.underline} consider realistic scheduling. It said:

> If it is determined over a period of 90 days or more that the flight
> schedule over a particular route cannot be completed by the pilots
> within the period of the scheduled flight time by more than 50 percent
> of the flights flown, then such schedules cannot be considered to
> adequately reflect the actual time required for flights over such
> route, and the carrier will be required to take corrective action.

In Interpretations Nos. 1990-25 and 1991-8 the Agency noted that the
determination of whether a schedule is realistic depends upon an
examination of all the facts and circumstances of a particular case. In
addition, we said that the original scheduling must be realistic and
represent a normal occurrence in the flight operations conducted by the
carrier. A schedule deemed a pretext, in an attempt to circumvent the
overall intent of the regulation, will not be considered to be
"realistic."

Interpretation No. 1990-25 involved an assessment of United Airlines'
(United) scheduling practices for flights operated under section
121.471(a)(4)'s 8 hour limit. The Agency relied on the carrier's data
for the month of June 1990 involving a total of 151 flights with the
crew scheduled between 7:50 and 7:59 hours of flight time, of which 101
(67%) were completed in scheduled flight time and 50 (33%) exceeded
scheduled flight time. We concluded that the flights were operated
within scheduled flight time approximately 67% of the time, and that
such a rate showed that United was scheduling realistically.

Interpretation No. 1991-8 involved an assessment of United's scheduling
practices for Pacific operations flights operated under section
121.483(a)'s 12 hour limit. The carrier's data for 1987 and 1988 winter
and summer operations for flights scheduled between 11 hours and 15
minutes and 1200 hours showed that for 1987, 94.9% of the summer flights
and 91.5% of the winter flights were completed within 12 hours. For
1988, the percentages of flights completed within 12 hours were 92.2%
for summer flights and 83.7% for winter flights. The Agency concluded
that the flights were operated within the scheduled flight time 85% to
95% of the time, and such a rate showed that United was scheduling
realistically.

The Flight Standards Service believes that the technological innovations
in communications, weather reporting, and flight planning have greatly
enhanced an air carrier's ability to accurately compute and predict
scheduled flight times. In light of the above discussion and the limited
factual information accompanying your request, the appropriate response
regarding the question you raise is for the FSDO to conduct a review,
consistent with Flight Standards Service's policy, of the carrier's data
for the last three calendar months, to determine compliance with section
121.503 (a) scheduled flight times. To the extent that the scheduled
flight times are determined to be realistic and to the extent that the
causes for the delays for Legs 1 and 2 were legitimately beyond the
control of the air carrier, then the carrier and the pilots are
permitted to complete Leg 3. This, of course assumes, that at that point
the crew is not so fatigued by the amount of the delays and the amount
of time on duty so as to create a careless or reckless situation in
violation of Section 91.13 of the regulations.

This letter was prepared by Joseph A. Conte, Manager, Operations Law
Branch and Constance M. Subadan, Attorney, Operations Law Branch. It was
coordinated with the Flight Standards Service at FAA Headquarters.

Sincerely,

Rebecca B. MacPherson

Assistant Chief Counsel

Regulations Division

Enclosures

[^1]: Section 121.503(a) states: A certificate holder conducting
    supplemental operations may schedule a pilot to fly in an airplane
    for eight hours or less during any 24 consecutive hours without a
    rest period during those eight hours.

[^2]: Section 121.505(a) states: If a certificate holder conducting
    supplemental operations schedules a pilot to

    fly more than eight hours during any 24 consecutive hours, it shall
    give him an intervening rest period at or

    before the end of eight scheduled hours of flight duty. This rest
    period must be at least twice the number of

    hours flown since the preceding rest period, but not less than eight
    hours. The certificate holder

    conducting supplemental operations shall relieve that pilot of all
    duty with it during that rest period.

[^3]: Section 121.471(g) states: A flight crewmember is not considered
    to be scheduled for flight time in excess of flight time limitations
    if the flights to which he is assigned are scheduled and normally
    terminate within the limitations, but due to circumstances beyond
    the control of the certificate holder (such as adverse weather
    conditions), are not at the time of departure expected to reach
    their destination within the scheduled time.

[^4]: Section 121.471(a)(4) states: No certificate holder conducting
    domestic operations may schedule any flight crewmember and no flight
    crewmember may accept an assignment for flight time in scheduled air
    transportation or in other commercial flying if that crewmember's
    total flight time in all commercial flying will exceed --

    ....

    \(a\) 8 hours between required rest periods.