For US student pilots
Class B clearance, and the Class C, D and Special VFR calls
The airspace classes differ in exactly one radio question: what do you need to hear before you cross the line? For Class B it is a clearance with the word “cleared” in it. For Class C and D it is a reply that uses your call sign. For a surface area below basic VFR minimums it is a Special VFR clearance.
The card below sets out each one, with the AIM paragraph, and the transponder codes that go with them.
Airspace classes & what you must do on the radio
US airspace is by class. The radio requirement rises with the class. [AIM chapter 3; 4-3-2; 4-4-6]
- Class B
- A clearance is required: you must hear “cleared into the Class Bravo” before entering. Expect a squawk first and “remain clear” until cleared. Mode C transponder within 30 miles of the primary airport.
- Class C
- Two-way radio communication with the approach control must be established before entry — a reply that uses your call sign. A transponder with altitude reporting is required.
- Class D
- Two-way communication with the tower before entering the surface area; initial call about 15 miles out. “Aircraft calling, stand by” does NOT establish communication — remain outside. [AIM 4-3-2 a]
- Class E surface area
- No radio requirement in VFR conditions; a Special VFR clearance below basic VFR.
- Special VFR
- A clearance to operate in a surface area below VFR minima: clear of clouds, at least 1 statute mile. Request it from the tower where there is one; state your intentions in enough detail to fit the traffic. [AIM 4-4-6]
NorCal Approach, Cessna One Seven Two Sierra Papa, one two miles south of Palo Alto, three thousand five hundred, request Class Bravo transition to San Carlos.
Transponder & squawk codes
- 1200
- VFR, unless ATC assigns a code. Altitude reporting on. [AIM 4-1-20 5 (a)]
- 7500
- Hijack. Never select it by accident — when changing codes, avoid passing through 7500, 7600 or 7700. [AIM 4-1-20 e]
- 7600
- Radio communications failure.
- 7700
- Emergency. Squawk it if you cannot immediately reach a facility. [AIM 6-3-2 a 2]
- Squawk (code)
- Set the code with altitude reporting. “Ident” — press the ident button, only when asked. “Squawk standby” — standby. “Squawk VFR” — 1200. [AIM 4-1-20 f]
Ask for the Bravo and hear what comes back
TowerTalk's Exercise I puts you at the edge of controlled airspace at a real US airport, with an approach controller who answers what you say and a grade with the AIM paragraph.
Related
Study aid, written in our own words from the FAA Aeronautical Information Manual (Change 3, 7/9/26) and the Pilot/Controller Glossary, with paragraph references so you can check each point. Last reviewed 9 September 2026; awaiting review by a US flight instructor. It does not reproduce those documents and is not a substitute for them — always defer to the AIM, the current FAA publications, your instructor and your examiner. TowerTalk is not approved or endorsed by the FAA.