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You take off from KFLL (Ft Lauderdale, FL) an hour before sunset in a B737. You're heading to KSEA (Seattle, WA).

4:35PM EST plus 6 hours 34 minutes is 11:09PM EST, or 8:09PM PST. Seattle sunset was 4:22PM PST.

Since the flight went west quickly it delayed sunset. Since it went north in the winter it hastened sunset.

So how does the flight crew split their day and night flying portions?

  • Record UTC when the PIC declares it to be night, split accordingly
  • A computer just tells them the answer
  • The flight crew already have ATP ratings, they don't care for detailed logging anymore
  • Something else

All of my flying has been roughly north/south at C172 speeds, so it hasn't really mattered more than the rounding error of recording in 0.1hr increments.

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    $\begingroup$ In practical terms, your third bullet ("The flight crew already have ATP ratings, they don't care for detailed logging anymore") is probably about right. I logged night & IMC faithfully until going to work for an airline, and I don't think I (or the automated systems that track hours & currencies) have logged a minute of either since then. At this level, nobody much worries about it any longer. $\endgroup$ – Ralph J Dec 24 '16 at 16:34
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I don't think many airline crew actually bother to log the day/night breakdown.

At my airline we have different pay rates for day and night flying, so we do care, but the company "Electronic Logbook" tracks the day/night breakdown for us. The system is not 100% accurate and we sometimes get paid more or less day or night then we actually fly in, but it tends to average out over the year.

In the summer, polar routes can be as much as 15 hour flights of daylight, while the same route in the winter can be 15 hours of night flying.

On some flights we will see the sun set, and then rise, and set again, as we chase the sun and our route changes from northwest bound to southwest bound.

enter image description here

Here are some samples of summer/winter, day/night Toronto to Hong Kong flying in my eLog:

enter image description here enter image description here

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Let me point out that for the purposes of logging flight time, night is defined under 14 CFR 1.1 as follows:

Night means the time between the end of evening civil twilight and the beginning of morning civil twilight, as published in the Air Almanac, converted to local time.

This means that sunset is not the deciding factor, but rather the published start and end times of civil twilight.

For the flight details you give, the transition to legal night would probably occur almost two hours into the flight somewhere near Little Rock, Arkansas, around 23:30 UTC at the end of local civil twilight. The specifics of that transition time and location will depend on ground speed, cruise routing, time spent in the departure routing and climb, and so on.


This same—or a similar—issue arises for slow aircraft over even relatively short distances. Any pilot flying any aircraft during the transition into or out of civil twilight where the time of civil twilight varies between the departure and destination points will face difficulty in determining exactly where and when the transition into legally loggable night time occurred.

When I was logging my first 100 hours of night time, I paid close attention to civil twilight on my flights so as to ensure I was not missing any loggable night time (and to ensure I wasn't incorrectly logging night time). Most of my 100 hours of night flight time took place in a C172 flying cross country into sunset or sunrise. To calculate the actual point where civil twilight began or ended, I consulted civil twilight tables based on my route of flight and interpolated the times to find the proximate location and time that night began or ended.

Now I care less about the amount of night time I have, and generally just log a leg as night if that leg took place entirely during night conditions. I suspect many professional pilots do the same.


14 CFR 61.51 requires a pilot to log:

(1) Training and aeronautical experience used to meet the requirements for a certificate, rating, or flight review of this part.

(2) The aeronautical experience required for meeting the recent flight experience requirements of this part.

The pilot must include the following information in that log:

(3) Conditions of flight—

(i) Day or night.

Logging night time is required if to be used toward a certificate such as the 100 hrs required the ATP. However, once beyond that requirement, logging night time is only required when documenting recency of flight experience such as night landings.

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  • $\begingroup$ Did you work out Little Rock by guess and check, or was there a more sophisticated way of getting the answer? $\endgroup$ – bartonjs Dec 24 '16 at 7:25
  • $\begingroup$ @bartonjs I calculated an approximate time by interpolation, considering departure time and cruise speed. I then checked the location to verify the end of civil twilight occurred at the right time. $\endgroup$ – J Walters Dec 24 '16 at 17:07

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