Airspace classes & requirements

This element is about the six airspace classes (A through G, with no F in the US). The DPE wants you to identify each class on a sectional, know what's required to enter it, what equipment the airplane needs, and what weather minimums apply to your flight.

Six classes, no F. One IFR-only (A). Three with explicit ATC entry rules (B/C/D). One mostly cooperative (E). One uncontrolled (G). The differences are in entry, equipment, pilot certificate, and weather minimums.

US airspace divides into controlled (A, B, C, D, E) and uncontrolled (G). Controlled airspace means ATC services are available; it does NOT automatically mean a clearance is required for VFR. The diagram below shows the classes from two angles: the "wedding cake" cross-section showing how altitude separates them, and a top-down view showing how Class B, C, and D appear on a sectional chart.

The vertical structure of the airspace system

The diagram shows the six classes from two angles — cross-section by altitude, top-down as they appear on a sectional. The detailed rules per class are in the H2s below; the structural takeaway:

• Class A caps the system at 18,000 MSL (IFR only above)
• Class B/C/D ring controlled towered airports at decreasing scope (busiest to smallest)
• Class E fills most of the controlled airspace below 18,000 — with a floor that varies (surface around non-towered IFR airports, 700 AGL where there's an approach, 1,200 AGL elsewhere)
• Class G is the uncontrolled remainder below the floor of E

Controlled airspace from the surface up

Class B. Most restrictive controlled airspace. Entry requires explicit clearance — "Cessna 12345, cleared into the Class Bravo airspace" — before crossing the lateral boundary or descending below the ceiling. Without those exact words, even with radio contact, you can't enter. Equipment: Mode C transponder, ADS-B Out, two-way radio. Pilot: at least private pilot, or student with a 61.95 endorsement for the specific airport (some Class Bs prohibit students entirely per 91.131(b)(2)). Weather: 3 SM and clear of clouds — the unique no-cloud-clearance rule because ATC is providing separation inside §91.131.

Class C. Two-ring cake around medium-sized towered airports: a 5 NM inner ring from the surface, a 10 NM outer "shelf" from 1,200 AGL, both to ~4,000 AGL. Entry requires two-way radio communication established with ATC — they must acknowledge by callsign. "N12345, standby" works; "aircraft calling, standby" does not. Equipment: Mode C + ADS-B Out. Pilot: any certificate level. Weather: 3-152 (3 SM, 500/1,000/2,000 from clouds) §91.130.

Class D. A single ring around smaller towered airports, surface to ~2,500 AGL within ~4 NM. Same two-way comm-established entry rule as Class C. No transponder/ADS-B requirement specific to Class D unless the Mode C veil applies from a nearby Class B. When the tower closes (part-time fields), the airspace typically reverts to Class E surface area or Class G. Weather: 3-152 §91.129.

Class E. Controlled airspace not A/B/C/D. No clearance required for VFR. Airport-vicinity operations follow the Class G traffic-pattern rules and the 4 NM / 2,500 AGL two-way radio comm requirement at towered E airports §91.127. Equipment: no Class-E-specific transponder rule below 10,000 MSL; at and above 10,000 MSL the standard 91.215 / 91.225 rule applies. Weather: 3-152 below 10,000 MSL; 5-111 at and above.

Class A and Class G airspace

Class A is the IFR-only high-altitude ceiling. All operations must be conducted under IFR per §91.135, with an ATC clearance and continuous two-way radio comm. VFR practically caps at 17,500 MSL (the highest legal odd-or-even-thousand-plus-500 below 18,000), so VFR can't reach the Class A floor. Without an instrument rating, IFR-equipped airplane, and clearance, Class A is off-limits.

Class G is the low-altitude uncontrolled remainder below the floor of Class E. ATC isn't providing service; see-and-avoid is paramount. Direction-of-turns at non-towered airports comes from §91.126: left turns by default unless markings indicate right; helicopters and powered parachutes avoid the fixed-wing flow. Weather minimums in Class G are the most permissive in the regulations and the trickiest table on the checkride — they vary by altitude AND time of day.

Equipment and pilot requirements

Transponder and ADS-B Out

A working Mode C transponder is required by §91.215 in Class A, B, and C airspace; within the Mode C veil (30 NM around primary Class B airports, surface to 10,000 MSL); and above 10,000 MSL with a 2,500 AGL exception. ADS-B Out per §91.225 is required in the same airspace as Mode C as of 2020 — the two rules cover overlapping coverage, but the technical equipment is distinct (transponder for Mode C, separate ADS-B Out for the broadcast).

Pilot certificate

• Class B — at least private pilot, OR student pilot with a 91.95 endorsement (with the specific Class B airports listed in 91.131(b)(2) prohibiting students entirely)
• Class C, D, E, G — any certificate level
• Class A — instrument-rated (because IFR operations only)

VFR weather minimums by class

The master rule lives in §91.155-class-c-d-e for Class C/D/E and §91.155-class-b for Class B; the at-or-above-10,000 MSL rule is §91.155-altitude; Class G specifics are §91.155-class-g.

Class	Visibility	Cloud clearance
Class A	N/A (IFR only)	N/A
Class B	3 SM	Clear of clouds
Class C / D / E (below 10,000 MSL)	3 SM	500 below, 1,000 above, 2,000 horizontal
Class E ≥ 10,000 MSL	5 SM	1,000 below, 1,000 above, 1 SM horizontal
Class G ≤ 1,200 AGL — day	1 SM	Clear of clouds
Class G ≤ 1,200 AGL — night	3 SM	500 / 1,000 / 2,000
Class G > 1,200 AGL and < 10,000 MSL — day	1 SM	500 / 1,000 / 2,000
Class G > 1,200 AGL and < 10,000 MSL — night	3 SM	500 / 1,000 / 2,000
Class G > 1,200 AGL and ≥ 10,000 MSL	5 SM	1,000 / 1,000 / 1 SM

Tap each class pill to see the rule update — the side-view diagram switches between the standard 500/1,000/2,000 overlay, the "Clear of clouds" badge (Class B and Class G day low altitude), and the 1,000/1,000/1 SM at-or-above-10,000 MSL variant. The status pill re-tones from rose (1 SM regime) through amber (3 SM) to emerald (5 SM).

The Class B "clear of clouds" rule is the major exception — because ATC is providing separation inside, the standard 500/1,000/2,000 doesn't apply. Class G is the most permissive AND the most varied. The 10,000 MSL transition shifts everyone to 5-111 because traffic at altitude tends to be faster and higher-energy.

Worked examples:

• VFR transition through Class B (KFFZ to KPHX). Departure from Falcon Field, Class D under the Phoenix Class B shelf. Initial: tower frequency, ground first, depart VFR. Hand-off: tower releases you to Phoenix Approach as you climb toward the shelf. Approach asks intentions, you request VFR transition through the Bravo at 4,500 to KPHX. Approach assigns a discrete squawk, confirms Mode C/ADS-B Out, and issues the magic words: "Cessna 12345, cleared into the Class Bravo airspace via the VFR corridor, maintain 4,500." Now you're in Class B legally — until that clearance, you stay below or outside the lateral boundary. Final: hand-off to Phoenix tower for landing. The sequence works because each transition is acknowledged: tower → approach (handoff), approach → Bravo entry (clearance), approach → tower (landing handoff). Miss the Bravo-entry clearance and you have to circle outside the boundary or back off.
• VFR cruise at 8,500 MSL in Class E — what mins apply? The airspace is Class E (default controlled airspace above the floor) and the altitude is below 10,000 MSL. Per the standard 91.155 table, the mins are 3 SM visibility with 500 below / 1,000 above / 2,000 horizontal from clouds (the "3-152" rule). If you climb to 10,500 MSL the rule shifts to 5 SM with 1,000 / 1,000 / 1 SM (5-111) — a substantial increase in visibility requirement. The 10,000 MSL boundary catches a lot of cross-country flights through marginal weather, and the visibility step from 3 to 5 SM often forces a lower cruise altitude or a deviation around the weather.