Class A Airspace Operations

FAR 91.135 Class A Airspace Operations

FAR 91.135 requires IFR flight, ATC clearance, two-way radio, and transponder/ADS-B in Class A airspace. Study guide for pilot students and checkride prep.

In Plain English

FAR 91.135 governs how you operate in Class A airspace — generally from 18,000 feet MSL up to FL600 in the U.S. The rule is strict because Class A is a high-altitude, high-speed environment where everyone must be talking to ATC and flying on instruments.

To operate in Class A, you must:

  • Fly under instrument flight rules (IFR) — VFR is not permitted.
  • Receive an ATC clearance before entering the airspace.
  • Carry a two-way radio and maintain continuous communication with ATC on an assigned frequency.
  • Be equipped with the required transponder (§ 91.215) and, after January 1, 2020, ADS-B Out (§ 91.225).

Why it matters: traffic in Class A includes airliners moving at high speeds, so positive ATC control and standardized IFR procedures are the only safe way to mix traffic.

If something fails — like an inoperative transponder — ATC can authorize a deviation. Planned deviations from this section must be requested in writing at least 4 days in advance.

Regulation Text
14 CFR § 91.135
§ 91.135 Operations in Class A airspace. Except as provided in paragraph (d) of this section, each person operating an aircraft in Class A airspace must conduct that operation under instrument flight rules (IFR) and in compliance with the following: (a)Operations may be conducted only under an ATC clearance received prior to entering the airspace. (b)Unless otherwise authorized by ATC, each aircraft operating in Class A airspace must be equipped with a two-way radio capable of communicating with ATC on a frequency assigned by ATC. Each pilot must maintain two-way radio communications with ATC while operating in Class A airspace. (c)Unless otherwise authorized by ATC, no person may operate an aircraft within Class A airspace unless that aircraft is equipped with the applicable equipment specified in § 91.215, and after January 1, 2020, § 91.225. (d)An operator may deviate from any provision of this section under the provisions of an ATC authorization issued by the ATC facility having jurisdiction of the airspace concerned. In the case of an inoperative transponder, ATC may immediately approve an operation within a Class A airspace area allowing flight to continue, if desired, to the airport of ultimate destination, including any intermediate stops, or to proceed to a place where suitable repairs can be made, or both. Requests for deviation from any provision of this section must be submitted in writing, at least 4 days before the proposed operation. ATC may authorize a deviation on a continuing basis or for an individual flight. [Docket 24458, 56 FR 65659, Dec. 17, 1991, as amended by Amdt. 91-314, 75 FR 30193, May 28, 2010]
Oral Exam Questions a DPE Might Ask
Q1What are the requirements to operate in Class A airspace?
Per FAR 91.135, you must operate under IFR, have an ATC clearance prior to entry, maintain two-way radio communications with ATC, and be equipped with the transponder and ADS-B Out equipment required by §§ 91.215 and 91.225.
Q2Can you fly VFR in Class A airspace?
No. FAR 91.135 requires all operations in Class A airspace to be conducted under IFR, unless ATC issues a specific deviation authorization under paragraph (d).
Q3If your transponder fails while you need to operate in Class A, what are your options?
Under FAR 91.135(d), ATC may immediately approve continued operation in Class A with an inoperative transponder, allowing you to proceed to your destination, intermediate stops, or to a place where suitable repairs can be made.
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FAR 91.135 — Operations in Class A Airspace