14.class-b-airspace. Class B Airspace
Class B airspace surrounds the nation's busiest airports by passenger enplanements and operations. It is depicted on VFR sectional charts and Terminal Area Charts (TAC) as solid blue lines, with each segment labeled by the floor and ceiling expressed in hundreds of feet MSL (e.g., 100/SFC means a ceiling of 10,000 feet MSL with a floor at the surface).
Shape and Dimensions
Class B airspace is individually tailored to the airport it protects, so no two are identical. The classic textbook description is an "upside-down wedding cake," consisting of a surface area centered on the primary airport surrounded by progressively wider shelves stacked above it. Most Class B airspace tops out at 10,000 feet MSL, although some (such as Denver) extend higher. Lateral dimensions typically extend out to about 30 NM from the primary airport, with a Mode C veil requiring an operable transponder with altitude reporting within 30 NM of the primary airport from the surface up to 10,000 feet MSL.
Operating Rules (14 CFR 91.131)
To operate within Class B airspace, a pilot must:
- Receive an ATC clearance prior to entering. The specific phrase "cleared into the Class Bravo" must be heard. Merely being in radio contact or receiving flight following is not sufficient.
- Operate a properly equipped aircraft. Required equipment includes a two-way radio, a Mode C transponder with altitude encoding, and ADS-B Out (per 14 CFR 91.225).
- Hold at least a private pilot certificate, OR be a student/recreational/sport pilot with the appropriate logbook endorsement under 14 CFR 61.95. Note that student pilots are prohibited from operating to, from, or through certain busy Class B primary airports listed in 14 CFR Part 91, Appendix D, Section 4.
Speed Limits
- Within Class B airspace: maximum 250 knots indicated airspeed (KIAS) below 10,000 feet MSL (the standard Part 91 rule).
- Beneath the lateral limits of Class B airspace, or in a VFR corridor designated through Class B: maximum 200 KIAS.
VFR Weather Minimums
Within Class B airspace the requirements are:
- 3 statute miles flight visibility
- Clear of clouds (no specific distance required)
This "clear of clouds" allowance reflects the fact that all aircraft within Class B are positively controlled and separated by ATC.
Separation Services
ATC provides separation between all aircraft (IFR-IFR, IFR-VFR, and VFR-VFR) operating within Class B airspace. VFR aircraft are typically separated by 1.5 NM lateral, 500 feet vertical, or visual separation, while IFR-IFR separation conforms to standard radar minima.
VFR Transition Procedures
A pilot wishing to transit Class B airspace VFR should contact the appropriate approach control facility well before reaching the boundary — generally about 20 NM out — and provide aircraft ID, type, position, altitude, and request. Example call:
"SoCal Approach, Cessna 12345, 25 miles east of LAX at 4,500, request Class Bravo transition westbound."
Until the controller specifically issues the words "cleared into the Class Bravo," the pilot must remain clear of the airspace. If the controller responds only with "standby," radio contact has been established but a clearance has not been issued — the pilot must not enter.
VFR Flyways, Corridors, and Transition Routes
To facilitate movement of VFR traffic around busy terminal areas, the FAA publishes:
- VFR Flyways — recommended flight paths shown on the reverse side of TACs, designed to avoid the most congested portions of Class B without requiring an ATC clearance (the pilot remains outside Class B).
- VFR Corridors — defined airspace through Class B in which a pilot may transit without a clearance (rare; the LAX "Special Flight Rules Area" is the classic example).
- Class B VFR Transition Routes — published routes through the airspace requiring a specific ATC clearance and discrete transponder code.
Equipment Requirements Summary
- Two-way radio capable of communicating with ATC on appropriate frequencies
- Operable transponder with Mode C (altitude encoding) — required within and above the lateral limits up to 10,000 feet MSL, and within the 30 NM Mode C veil
- ADS-B Out meeting 14 CFR 91.227 performance requirements
- For IFR operations, a VOR or suitable RNAV (GPS) navigation receiver
Example: Determining Floor and Ceiling
If a sectional chart shelf is labeled 100/40, the floor of that shelf is 4,000 feet MSL and the ceiling is 10,000 feet MSL. A VFR pilot flying at 3,500 feet MSL beneath the shelf is outside Class B, but must still remain at or below 200 KIAS and be aware of converging traffic descending into or climbing out of the primary airport.
Mastery of Class B procedures is essential because deviation can result in a pilot deviation report, certificate action, and — more importantly — loss of separation with high-performance traffic.