How to Read a Sectional Chart (Part 107)

Airspace Classification and Operating Requirements is 20% of the current FAA Part 107 knowledge test — second only to Regulations (UAG_Information_Bulletin.pdf, p. 4) — and nearly all of it comes down to one skill: reading a sectional chart. Every figure on this page is a real excerpt from the FAA’s own Airman Knowledge Testing Supplement (FAA-CT-8080-2H), the same book handed to applicants at the test center. Tap any chart to pinch-zoom and pan, the same way you’ll need to at the testing center.

Airspace class from border color and line style

The FAA’s own chart legend defines exactly one line style per airspace class, and mixing them up is the single most common chart-reading mistake:

• Class B — solid blue line
• Class C — solid magenta (dark pink/red) line
• Class D — dashed blue line
• Class E, surface area — dashed magenta line
• Class E, floor 700 ft. above surface — fading (vignette) magenta band
• Class E, floor 1,200 ft. or greater above surface, or abutting Class G — fading (vignette) blue band
• Class G — no boundary line at all; it’s simply what’s left over

(FAA-CT-8080-2H, Legend 1, p. 1-1.)

The FAA’s study guide gives the typical vertical dimensions behind each line style: Class B generally runs from the surface to 10,000 ft. MSL around the nation’s busiest airports; Class C generally runs from the surface to 4,000 ft. above the airport elevation, usually a 5 NM surface core plus a 10 NM shelf from 1,200–4,000 ft.; Class D generally runs from the surface to 2,500 ft. above the airport elevation; and Class E is every other piece of controlled airspace, most often based at 700 ft. or 1,200 ft. AGL (remote_pilot_study_guide.pdf, pp. 5–6).

Figure 20 shows this in practice around Norfolk International (ORF). The inner ring is charted “40” over “SFC” — a ceiling of 4,000 ft. MSL sitting directly on the surface, meaning Class C reaches the ground there. The outer ring is charted “40” over “12” — the same 4,000 ft. MSL ceiling, but now with a floor of 1,200 ft. MSL instead of the surface. A small UA flying at 300 ft. AGL under that outer shelf is below the floor and isn’t in Class C at all, so 14 CFR § 107.41’s ATC-authorization requirement doesn’t apply there — even though the same magenta ring surrounds both segments on the chart (sport_rec_private_akts.pdf, Figure 20, p. 2-19; 14-cfr-107.txt, § 107.41).

Try this yourself in the sectional chart drill →

Reading altitude floors and ceilings from stacked numbers

Class B, C, and D shelves are always labeled with a number stacked over either “SFC” or another number, in hundreds of feet MSL. The top number is always the ceiling; the bottom is the floor. Class E uses the same convention where a floor sits above 700 ft.: a bare number like “2400 MSL” or “4500 MSL” marks where a higher Class E floor begins, to differentiate it from the default 700 ft. or 1,200 ft. AGL base (FAA-CT-8080-2H, Legend 1, p. 1-1).

Figure 25 shows Dallas/Fort Worth International (DFW), where the innermost Class B shelf is charted “110/SFC” — a ceiling of 11,000 ft. MSL sitting on the surface. Because the floor is the surface itself, there’s no altitude low enough to escape the authorization requirement directly over the airport; a small UA anywhere in that segment needs ATC authorization under § 107.41 before flying at all (sport_rec_private_akts.pdf, Figure 25, p. 2-24; 14-cfr-107.txt, § 107.41).

Special-use and other airspace

Special-use airspace restricts or warns rather than classifying controlled airspace outright. The FAA study guide defines the ones you’ll see on a sectional: prohibited areas (“P” + number, all flight barred), restricted areas (“R” + number, hazardous nonparticipating activity — permission from the using/controlling agency required before entry), warning areas (“W” + number, the same hazards as a restricted area but over water outside U.S. jurisdiction), military operations areas (charted by name, not number), and alert areas (“A” + number, high-volume training traffic) (remote_pilot_study_guide.pdf, pp. 7–9).

Figure 20 again shows two of these side by side off Virginia Beach: “WARNING W-50B” marks hazardous activity extending seaward from the coast, and the small hatched “R-6606” nearby is a restricted area. 14 CFR § 107.45 requires permission from the using or controlling agency before operating a small UA inside R-6606 — the same rule that applies to any restricted area (sport_rec_private_akts.pdf, Figure 20, p. 2-19; 14-cfr-107.txt, § 107.45).

“Other airspace areas” cover everything else a sectional marks that isn’t a classification or a special-use boundary: military training routes, temporary flight restrictions, terminal radar service areas, national security areas, and published VFR routes among them (remote_pilot_study_guide.pdf, p. 9). Figure 21 shows a military training route labeled “IR644-649” — the “IR” prefix identifies an IFR military training route, flown below 10,000 ft. MSL at speeds over 250 knots; a “VR” prefix (as on Figure 23 in the chart drill) marks the VFR equivalent instead (sport_rec_private_akts.pdf, Figure 21, p. 2-20; remote_pilot_study_guide.pdf, p. 10).

Obstacle heights: MSL vs. AGL

Every charted obstruction carries two numbers, and the legend defines which is which: the plain number is the elevation of the top above mean sea level (MSL), and the parenthetical number underneath is the height above ground (AGL) (FAA-CT-8080-2H, Legend 1, p. 1-1).

Figure 24 marks an obstruction near Klondike, Texas as “935” over “(425)” — the top of the structure sits 935 ft. MSL, and it rises 425 ft. above the ground beneath it (sport_rec_private_akts.pdf, Figure 24, p. 2-23). That AGL figure is the one that matters for part 107: operations are generally capped at 400 ft. AGL, with an exception for flying near a taller structure, so knowing a nearby obstacle’s actual height above the ground — not its MSL elevation — is what tells you whether that exception applies (14-cfr-107.txt, § 107.51(b)).

What changes on October 26, 2026

Starting October 26, 2026, the UAG knowledge test begins drawing image-based questions directly from current FAA VFR sectional charts, in addition to the figures in the printed testing supplement used throughout this guide (September_2026_Special_Edition.pdf, p. 6). The supplement hasn’t been withdrawn and still has no announced removal date — it’s an addition, not a replacement, so everything above still applies at the test center.

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Keep practicing with the real figures above, or go symbol by symbol in the chart legend reference. Jump into the sectional chart drill to try these skills yourself, browse practice questions by area, or head back to the chart hub.

Frequently asked questions

What do the colored lines on a sectional chart mean?

They mark the floor and class of controlled airspace: solid blue for Class B, solid magenta for Class C, dashed blue for Class D, and dashed or fading magenta/blue for Class E, depending on its floor (FAA-CT-8080-2H, Legend 1, p. 1-1).

Are these the same chart figures used on the real exam?

These figures come from FAA-CT-8080-2H, the Airman Knowledge Testing Supplement issued at the test center. Starting October 26, 2026, the exam also draws separate image-based questions directly from current VFR sectional charts (September_2026_Special_Edition.pdf, p. 6).

Is the obstacle height number measured from the ground or from sea level?

Both appear together: the plain number is height above mean sea level, and the number in parentheses underneath is height above ground level (FAA-CT-8080-2H, Legend 1, p. 1-1).

Do I need ATC authorization everywhere inside a magenta or blue ring?

Not always — it depends on the floor charted for that segment. The same Class C ring can require authorization at the surface in one spot and not at all 300 ft. AGL a few miles away, if the floor there is charted at 1,200 ft. MSL instead of the surface (sport_rec_private_akts.pdf, Figure 20, p. 2-19; 14-cfr-107.txt, § 107.41).