Private pilot · ACS PA.I.E
National Airspace System
This task is about knowing where you are in the airspace, what each class requires, and how much weather you need to stay VFR.
Use your sectional: the boundaries and altitudes are all on it.
Why this one matters
Airspace exists to separate traffic and protect people on the ground. Busting a Class B shelf, wandering into a TFR, or pushing VFR minimums into cloud puts you where other airplanes and ATC don't expect you. Knowing the boundaries, the entry requirements and the weather minimums is how you fly predictably and safely around everyone else.
Can’t miss
- •Class B: an ATC clearance ("cleared into the Class Bravo"), a two-way radio, a Mode C transponder and ADS-B Out; 3 statute miles and clear of clouds.(14 CFR 91.131, 91.155)
- •Class C: establish two-way radio communication before entering, plus a Mode C transponder and ADS-B Out; 3 miles, 500 below, 1,000 above, 2,000 horizontal.(14 CFR 91.130, 91.155)
- •Class D: establish two-way radio communication before entering; 3 miles, 500 below, 1,000 above, 2,000 horizontal.(14 CFR 91.129, 91.155)
- •Class E below 10,000 MSL: 3 miles, 500/1,000/2,000. At or above 10,000 MSL: 5 miles, 1,000 below, 1,000 above, 1 mile horizontal.(14 CFR 91.155)
- •Class G at or below 1,200 AGL by day: 1 mile and clear of clouds. At night: 3 miles, 500/1,000/2,000.(14 CFR 91.155)
- •Speed (indicated): 250 knots below 10,000 MSL; 200 knots at or below 2,500 AGL within 4 nm of a Class C or D primary airport (not inside Class B, where 250 applies); and 200 knots in the airspace under a Class B shelf or in a VFR corridor through it.(14 CFR 91.117(a)-(c))
- •Check TFRs and NOTAMs before every flight; prohibited areas are off-limits, restricted areas need permission.(14 CFR 91.103, 91.133, 91.137-91.145)
What you should know
The classes and what they require K1 · R1
- Class A: 18,000 feet MSL up to FL600. No VFR at all: an instrument-rated pilot on an IFR flight plan with an ATC clearance, a two-way radio, a Mode C transponder and ADS-B Out.(AIM chapter 3, Airspace; 14 CFR 91.135, 91.215, 91.225)
- Class B generally extends from the surface to 10,000 feet MSL around the busiest airports, in individually tailored layers shaped to contain the instrument procedures.(AIM chapter 3, Airspace)
- Class B: around the busiest airports, shaped like an upside-down wedding cake. Needs an ATC clearance, a two-way radio, a Mode C transponder and ADS-B Out. A private pilot may enter; student pilots need an endorsement, and some primary airports don't allow student operations.(14 CFR 91.131)
- Mode C and ADS-B Out are also required within 30 nm of a Class B primary airport (the Mode C veil), in and above Class C up to 10,000 MSL, and in Class E at or above 10,000 MSL (except at or below 2,500 AGL).(14 CFR 91.215, 91.225)
- Class C: typically a 5 nm core from the surface to 4,000 feet above the airport and a 10 nm shelf from 1,200 feet. The shelf's ceiling is also 4,000 feet above the airport. Around it is a procedural Outer Area, normally 20 nm, uncharted, where participation isn't required the same way. Charted Class B and C altitudes are MSL, even though the textbook describes them above the airport.(14 CFR 91.130; AIM 3-2-4)
- Two-way communication for Class C and D: a reply using your call sign, even "[call sign], stand by", establishes it and you may enter, unless the reply tells you to remain outside ("[call sign], remain outside the Class Charlie and stand by"). A reply without your call sign ("aircraft calling Approach, stand by") does not establish it: stay out.(14 CFR 91.130(c), 91.129(c); AIM 3-2-4, 3-2-5)
- Class D: around towered airports, typically up to 2,500 feet above the airport. Establish two-way communication before entering. Class D itself requires only the radio: no transponder or ADS-B Out (unless other rules, such as the Mode C veil, apply). When the tower closes, it usually becomes Class E or G; check the Chart Supplement.(14 CFR 91.129; AIM 3-2)
- Class E: controlled airspace that isn't A, B, C or D. It may start at the surface, at 700 or 1,200 feet AGL, or at other altitudes. No communication is required for VFR.(AIM chapter 3, Airspace)
- Class G: uncontrolled airspace below Class E.(AIM chapter 3, Airspace)
VFR weather minimums K1
- Class B: 3 statute miles, clear of clouds.(14 CFR 91.155)
- Class C, D and E below 10,000 MSL: 3 miles; 500 feet below, 1,000 above, 2,000 horizontal from clouds.(14 CFR 91.155)
- Class E at or above 10,000 MSL: 5 miles; 1,000 below, 1,000 above, 1 mile horizontal.(14 CFR 91.155)
- Class G at or below 1,200 AGL: day 1 mile, clear of clouds; night 3 miles, 500/1,000/2,000 (or 1 mile and clear of clouds in a traffic pattern within half a mile of the runway).(14 CFR 91.155)
- Class G above 1,200 AGL below 10,000 MSL: day 1 mile, 500/1,000/2,000; night 3 miles, 500/1,000/2,000. Above 10,000 MSL: 5 miles, 1,000/1,000/1 mile.(14 CFR 91.155)
- Two separate rules, except under special VFR (91.157): you may not fly under VFR beneath a ceiling of less than 1,000 feet anywhere within the lateral limits of a surface area of controlled airspace (91.155(c)); and you may not take off, land, or enter the traffic pattern in a Class B, C, D or E surface area unless the ground visibility there is at least 3 statute miles, or the flight visibility is if ground visibility isn't reported (91.155(d)).(14 CFR 91.155(c)-(d); 91.157)
Reading the chart K2
- Class B: solid blue lines. Class C: solid magenta. Class D: dashed blue. Class E to the surface: dashed magenta.(FAA Aeronautical Chart User's Guide)
- Class E starting at 700 feet AGL: the faded magenta edge (vignette). Starting at 1,200 feet AGL: the faded blue edge.(FAA Aeronautical Chart User's Guide)
- Altitude labels like 80/40 in Class B or C mean a ceiling of 8,000 and a floor of 4,000 feet MSL.(FAA Aeronautical Chart User's Guide)
Special use airspace, TFRs and other areas K3
- Prohibited areas: flight not allowed. Restricted areas: not allowed when active without permission from the controlling agency.(14 CFR 91.133; AIM 3-4)
- Military operations areas (MOAs): VFR flight is allowed, but watch for fast military traffic and ask ATC whether they're active. Warning areas extend from 3 nm outward from the U.S. coast with activity that may be hazardous; the U.S. doesn't have sole jurisdiction, so no permission is needed, but use caution. Alert areas have a high volume of pilot training or unusual aerial activity: use caution. Controlled firing areas aren't charted, because the activity stops when an aircraft approaches. National security areas: you are asked to avoid them voluntarily, and flight may be temporarily prohibited.(AIM 3-4-1 to 3-4-8)
- Other areas: a TRSA isn't an airspace class (its primary airport is Class D); VFR participation is voluntary and gives radar service. Military training routes: IR flown under IFR, VR under VFR; four-digit routes stay at or below 1,500 AGL, three-digit routes have a segment above it, and military aircraft may exceed 250 knots below 10,000 MSL, so cross them with vigilance and don't follow them. Also know ADIZ rules (a flight plan, a discrete code and two-way radio), parachute jump areas, and published VFR flyways and transition routes.(PHAK (FAA-H-8083-25C), Ch. 15; AIM 3-5)
- Temporary flight restrictions (TFRs) cover VIP movements, stadiums, fires and other events. They're in the NOTAMs; check them before every flight.(14 CFR 91.137-91.145; AIM 3-5)
- Special flight rules areas, like the Washington, DC SFRA, have their own rules and required training.(14 CFR Part 93; 91.161)
Special VFR K4
- Special VFR lets you operate below VFR minimums within the surface area of controlled airspace, below 10,000 MSL, with an ATC clearance. You must ask for it; ATC doesn't offer it.(14 CFR 91.157)
- You need at least 1 statute mile flight visibility and must stay clear of clouds. To take off or land, ground visibility must be at least 1 statute mile (flight visibility, if ground visibility isn't reported). Fixed-wing special VFR isn't allowed at the airports in Part 91, Appendix D, Section 3 (charted "NO SVFR").(14 CFR 91.157; Part 91, Appendix D)
- At night (sunset to sunrise), special VFR requires the pilot to be instrument rated and current, and the airplane equipped for IFR under 91.205(d).(14 CFR 91.157(e))
Scenarios
Decide what you would do first, then see the worked answer.
You call Approach to transit a Class B. The controller says: "N123AB, radar contact, maintain VFR at or below 3,500."
Can you enter the Class B? See the worked answer
No. You need to hear "cleared into the Class Bravo airspace". Radar contact isn't a clearance. Stay outside until you're cleared.
14 CFR 91.131
Your home airport's tower closes at 9 p.m. You plan to land at 10 p.m.
What airspace will it be, and how do you find out? See the worked answer
Usually Class E or G after the tower closes. The Chart Supplement lists the hours and what the airspace becomes. Use the CTAF.
AIM 3-2; Chart Supplement
The METAR at a Class D airport shows visibility 2 miles in mist and a ceiling of 800 feet. You want to land there.
What are your options? See the worked answer
Under basic VFR you can't enter the surface area for landing. You could request special VFR by day (1 mile, clear of clouds), if you're comfortable and it's within your minimums; otherwise divert.
14 CFR 91.155(c), 91.157
Your route crosses a MOA. Flight Service says it's active.
Can you fly through? See the worked answer
VFR flight through a MOA is legal, but military aircraft may be maneuvering fast. Consider routing around, or ask ATC for traffic information while crossing.
AIM 3-4
Common mistakes
Treating "radar contact" as permission to enter Class B.
Only "cleared into the Class Bravo" is a clearance.
Instead: Wait for the explicit clearance.
Mixing up the cloud clearances.
Class B is clear of clouds; C, D and E are 500 below, 1,000 above, 2,000 horizontal.
Instead: Learn the table by class and altitude, and day versus night in Class G.
Skipping a TFR check on a short local flight.
TFRs pop up for VIPs, fires and stadiums, sometimes the same day.
Instead: Check NOTAMs and TFRs right before every flight.
Now train it
Say it out loud, hear it asked, and take the quick check in this lesson’s practice pack. It tracks your shaky spots.
Got it?
When it feels solid, practice national airspace system out loud with our examiner.
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Sources
- 14 CFR Part 91: 91.117, 91.126-91.135, 91.137-91.145, 91.155, 91.157, 91.215, 91.225
- AIM: Chapter 3, Airspace
- Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C): Airspace
- FAA Aeronautical Chart User's Guide
Study aid, not FAA guidance. Regulations change; check the current text at eCFR and the ACS. Checked against current sources 2026-11-12.