2.1 National Airspace System Overview
Key Takeaways
- The NAS uses six ICAO classes: A through E are controlled airspace, G is uncontrolled.
- Part 107 needs authorization for Class B, C, D, and the surface area of Class E; never for Class G.
- Prohibited Areas (P-XX) never permit flight; Restricted Areas (R-XX) require the controlling agency's permission.
- Airspace and chart reading make up roughly 25% of the 60-question Part 107 exam.
- Check the FAA NOTAM system for active TFRs before every flight; violations carry severe penalties.
The National Airspace System
The National Airspace System (NAS) is the network of airspace, navigation aids, airports, and air traffic management that keeps every aircraft over the United States separated and safe. For the remote pilot in command (Remote PIC), airspace is not abstract trivia: the FAA's Airman Certification Standards (ACS) make airspace, sectional-chart reading, and authorization one of the most heavily tested areas. Expect roughly 25% of the 60-question exam to touch airspace, and you must answer 42 of 60 (70%) correctly within the 2-hour window to pass.
The Six ICAO Classes
The U.S. adopted the International Civil Aviation Organization (ICAO) lettered classes. Class F is not used domestically, so you study A, B, C, D, E (controlled) and G (uncontrolled).
| Class | Type | Where it is | ATC service | Part 107 relevance |
|---|---|---|---|---|
| A | Controlled | 18,000 ft MSL up to FL600 | Required, IFR only | Irrelevant (far above the 400 ft AGL ceiling) |
| B | Controlled | Busiest airports (e.g., ATL, LAX) | Required | Authorization required |
| C | Controlled | Radar-equipped busy airports | Required | Authorization required |
| D | Controlled | Towered airports | Required when tower open | Authorization required |
| E | Controlled | Transition/en route, some surface areas | As needed | Authorization required ONLY for surface areas |
| G | Uncontrolled | Surface up to the base of overlying E | None | No authorization needed |
Controlled vs. Uncontrolled
Controlled airspace (A-E) means ATC provides some service and aircraft must meet equipment and communication rules. The Part 107 trigger is narrow: you need an authorization only when the controlled airspace touches the surface at an airport — Class B, C, D, or a Class E surface area. Class G is uncontrolled; ATC provides no separation and Part 107 drones fly without authorization, though every other rule (400 ft AGL ceiling, visual line of sight, daylight/twilight lighting) still applies.
The Inverted Wedding Cake
Controlled airspace around an airport is drawn as an inverted (upside-down) wedding cake — narrow at the surface, wider in higher shelves. A drone flying at 350 ft AGL several miles from a Class B primary airport may sit under an outer shelf that begins at 3,000 ft MSL, placing the drone in Class G. Reading the floor/ceiling labels on each shelf is the skill the exam tests.
Special Use Airspace (SUA)
| SUA type | Chart symbol | Purpose | Part 107 rule |
|---|---|---|---|
| Prohibited Area | P-XX, blue hatching | National security/welfare | Flight NEVER permitted |
| Restricted Area | R-XX, blue hatching | Weapons firing, missiles | Permission required from controlling agency |
| Warning Area | W-XX, blue hatching | Hazards over international waters | Caution; outside U.S. sovereign airspace |
| Military Operations Area (MOA) | Magenta hatching | Military training | No FAA authorization, but use extreme caution |
| Alert Area | A-XX, magenta hatching | Heavy training or unusual activity | No authorization; caution |
| Controlled Firing Area (CFA) | Not charted | Live firing that stops when aircraft approach | Not charted; activity ceases for traffic |
Common Traps
- A MOA is not a no-fly zone — drones need no FAA authorization there, only heightened vigilance. Exam writers love to mark it as "authorization required."
- A Restricted Area is not the same as a Prohibited Area: restricted means "ask the controlling agency," prohibited means "never."
- A Controlled Firing Area is never shown on the chart because its activity stops the moment aircraft are detected, so it needs no charted boundary.
How a Remote Pilot Uses Airspace Knowledge
Knowing the classes is not an academic exercise; it drives three concrete preflight decisions. First, do I need an authorization? That answer depends entirely on whether surface-touching controlled airspace is present, which is why every airspace question ultimately reduces to identifying the floor of the airspace over your launch point. Second, what altitude can I get? Even where authorization is available, the ceiling may be far below the regulatory 400 ft AGL, so a roof inspection that needs 380 ft may be impossible near a busy airport.
Third, what hazards share this airspace? Manned aircraft on approach descend through low altitudes near airports, gliders and ultralights frequent some areas, and military traffic transits MOAs at high speed, so airspace identity also tells you where to watch the sky.
Memory Framework for the Exam
A reliable way to keep the classes straight under time pressure is to anchor on the busiest-to-least-busy ordering: A (high-altitude jet routes), B (mega-hubs), C (radar-served regional hubs), D (any tower), E (controlled fill, mostly above you), G (everything left over). Pair that with the authorization rule: only the airspace that reaches the surface at an airport demands an authorization.
A drone pilot rarely cares about Class A because it begins at 18,000 ft MSL, vastly above the 400 ft AGL ceiling, and the exam frequently uses Class A as a distractor in "which class do you need authorization for" questions precisely because new pilots over-think it.
Worked Scenario
You plan to photograph a warehouse roof. The sectional shows the site lies under a Class C outer shelf whose floor is 1,200 ft AGL, with no surface area reaching your location. Because the controlled airspace does not touch the surface where you stand, you are in Class G beneath it and need no authorization to fly at 350 ft AGL. Change one fact — move the warehouse inside the 5 NM Class C inner core that reaches the surface — and now you do need an authorization. The lesson the exam rewards is reading the floor of the airspace directly above the launch point, not the airspace label seen elsewhere on the chart.
For the exam: if controlled airspace touches the surface at an airport, you need authorization. Class G needs none. Prohibited = never; Restricted = permission; MOA/Alert = caution only.
In which class of airspace can a Part 107 drone operate WITHOUT prior authorization?
Which Special Use Airspace requires permission from the controlling agency but is not an absolute no-fly zone?