Civil twilight and night

Three states of the sky

The sky, as far as Part 107 is concerned, is in one of three states, and your obligations change at the boundaries. In daylight, between official sunrise and official sunset, there is no lighting requirement. In civil twilight, the half hour before sunrise and the half hour after sunset, the aircraft must carry a lit anti-collision light. At night, everything between the end of the evening twilight and the start of the morning twilight, you need the light and one more thing about you, the pilot.

14 CFR § 107.29(a), (b), (c)

An astronomer would define twilight by geometry: civil twilight ends when the center of the sun is 6 degrees below the horizon. That is a fine definition for an almanac and a poor one for a person standing in a parking lot with a drone in their hands. Nobody in the field can see six degrees of solar depression. A pilot needs a number they can add to a time they can look up, so the FAA picked one: 30 minutes before official sunrise, 30 minutes after official sunset. Outside Alaska, that is the whole definition.

14 CFR § 107.29(c)(1), (c)(2)

The fixed number is a convenience, and it is slightly wrong in both directions depending on where and when you stand. At mid-latitudes near the equinoxes it is close to the geometric answer. Closer to the equator the sun drops faster and real twilight is shorter; farther north, and in winter, it lingers longer. Alaska is where this breaks completely. In summer at Anchorage’s latitude the sun may never get 6 degrees below the horizon at all, so a flat 30 minutes would invent a night that the sky does not have. For that reason the regulation hands Alaska to the Air Almanac and its own definition of civil twilight.

14 CFR § 107.29(c)(3) · AC 107-2A ¶ 5.7

What each state asks of you

Requirements by state of the sky

Day (sunrise to sunset)	No anti-collision light required	AC 107-2A ¶ 5.7.2.2
Civil twilight (30 min before sunrise, 30 min after sunset)	Anti-collision light visible for at least 3 SM	14 CFR § 107.29(b)
Night	Same light, plus a remote PIC who completed the initial test or recurrent training after April 6, 2021	14 CFR § 107.29(a)
Light intensity	May be reduced for safety; may never be extinguished	14 CFR § 107.29(a)(2), (b)

Notice what changes between the rows. The light is the same in twilight and at night; the pilot’s training is the only addition. The training condition exists because the knowledge test and recurrent training were updated on that date to cover night physiology and night visual illusions, the subject of the next section. Today it takes the training and the light.

14 CFR § 107.29(a)(1) · AC 107-2A ¶ 5.7.2, 5.7.2.1

The light itself has three requirements: it must be lit, visible for at least 3 statute miles, and have a flash rate sufficient to avoid a collision. You may lean on the manufacturer’s statement that the light is visible for 3 miles, but the checking is still yours: you remain responsible for confirming it works, that it reaches 3 miles, and that the flash rate suits where you are flying.

14 CFR § 107.29(a)(2) · AC 107-2A ¶ 5.7.2

Why may you dim it but never switch it off? A strobe a few feet from your face can wash out your view of the aircraft and make it hard to judge where it is, how fast it is moving, or how it is tilted. If the light hurts your ability to see the aircraft, you are less able to meet your other obligations, so the rule lets you turn it down. But the light is for everyone else’s eyes, and a light that is off cannot be seen by anyone who might be looking for you.

14 CFR § 107.29(a)(2) · AC 107-2A ¶ 5.7.2.2

The human side of the dark

The regulation requires a light; physiology decides whether you can use it. The eye has two kinds of receptors. Cones handle color and fine detail in good light and are packed at the center of your vision. Rods handle dim light and movement, and they sit around the outside. At night the cones stop being useful, which means the very center of your vision is the weakest part. Look straight at a dim aircraft and it can vanish.

FAA-H-8083-25C, Ch. 17

So you look slightly off to one side of what you want to see, letting the image land on the rods. Hold it there and the image fades after a couple of seconds, so shift between nearby points rather than staring. The handbook gives about 5 to 10 degrees off center for this.

FAA-H-8083-25C, Ch. 17

Rods are also slow. Fully adapting them to darkness takes about 30 minutes, and a bright light can destroy that adaptation and start the clock again. That is the trap in a very ordinary routine: you assemble the aircraft under a work light or a headlamp, preflight it, walk into the dark, and launch. You are seeing as if you just stepped out of a bright room, because you did. Plan the preflight with dim light, or give yourself the half hour before you fly.

FAA-H-8083-25C, Ch. 17

Keeping the aircraft in sight is harder than this makes it sound, and the rule does not relax at night. Section 107.31 still requires you to see the aircraft with unaided vision in order to know where it is, what its attitude, altitude, and direction are, and what is around it. In the dark, reduced light and contrast make that difficult, so the FAA expects that you will usually need to shrink your operating area. And the light on the aircraft does not satisfy the rule for you: you cannot rely solely on the anti-collision light, or on the telemetry on your screen, or on both together.

14 CFR § 107.31(a) · AC 107-2A ¶ 5.9.3

A light against a black sky tells you a light is there. It does not tell you which way the aircraft is pointing, how high it is, or whether it is about to meet a branch. A stationary light stared at in the dark can also appear to drift, which is a good reason to keep your scan moving.

Where the times come from

The sunrise and sunset in the regulation are official ones, as published in the Air Almanac for your location and converted to local time. The AC points to the U.S. Naval Observatory, which publishes tables you can customize for a place, and the general idea is the same for any reliable source: it must give the sun’s times for where you will be flying, not for a city that happens to be nearby. The weather app on your phone is fine for planning and for the dial below, as long as you know it is somebody’s calculation of the same thing. If a flight is close to the line, such as landing a few minutes before the twilight ends, trust a published table over a screenshot, and leave margin.

AC 107-2A ¶ 5.7

Two cautions. Times are local, so check the time zone and daylight saving time. And the times move from day to day, so a sunset you remember from last month is worse than no number at all.

Using the dial

The dial below takes a place and a date, and draws the day as a ring. Day is the pale arc, the two civil twilight bands are orange, and night is dark ink. The thin ring just inside it shows the astronomer’s sun-6-degrees-below version for comparison. Drag the hand anywhere on the ring and the readout tells you which state you are in and what lighting that requires. Since it opens on today’s date, set the date yourself for each of these.

First, a June evening in Washington, DC. Pick June 21 and drag the hand to sunset, which falls near 8:37 pm. Slide forward and you cross into the orange band, where the light is required, and out of it about 9:07 pm. After that you are in night. The inner ring ends within a couple of minutes of the orange band, so here the astronomer and the regulator agree.

Second, the same date in Anchorage. At that latitude sunset is near midnight and the next sunrise comes around 4:20 am. The regulatory bands still draw as 30 minutes each, so the dial shows a few hours of ink, but the dial does not claim this is the Alaska answer; the note beneath it says as much. The inner ring may look broken or missing, because the sun never gets 6 degrees below the horizon. The astronomer’s twilight never ends that night, which is exactly why the regulation does not use the flat 30 minutes there.

14 CFR § 107.29(c)(3)

Third, a December afternoon in Seattle. Pick December 21 and go to sunset, around 4:20 pm. A pilot finishing a job at 4:45 pm is still in civil twilight and needs only the light. At 5:00 pm the hand is in the ink, and the training condition now applies even though the clock says late afternoon. Look at the inner ring: the astronomical twilight runs about 36 minutes there, longer than the fixed 30, so the regulatory number lets night begin a little before the sky is truly dark.

Having moved the hand around, notice how little of the ring is the thing that requires nothing. In winter at Seattle, daylight is only a bit over eight hours. A plan of “I’ll fly after work” quietly becomes a night operation.

14 CFR § 107.29(a), (b)

How the test asks it

FAA sample questions 27, 40, 43 · 14 CFR § 107.29(a)(2), (b) · FAA-H-8083-25C, Ch. 17

The common slip is to treat the 30-minute window as part of the day. It is not. A question that mentions a time after sunset is asking about the light before it asks about anything else, and a question about night adds the training condition.

For the rest of the rules around this one, return to the Regulations chapter, where the night section sits among the operating limits. For the eye, the illusions, and flying fit, go to the Operations chapter.