§ 91.21 Portable electronic devices.

Section 91.21 governs the use of portable electronic devices (PEDs) aboard U.S.-registered civil aircraft. The reg lives in tension with modern reality — billions of PEDs, ubiquitous Wi-Fi, and an FAA framework written before smartphones existed. The 2013 FAA policy shift created the regulatory path for in-flight use of most PEDs during all phases of flight, but § 91.21 itself remains the operational anchor.

The general prohibition (paragraph a): No person may operate (and no operator may allow) any PED on a U.S.-registered civil aircraft operated by an air carrier or commercial operator, or any aircraft operating under IFR. The prohibition is the default — the exceptions are how PEDs become usable.

The exception that swallows the rule (paragraph b): Paragraph (b)(5) allows "any other portable electronic device that the operator of the aircraft has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used." That single clause is the regulatory hook the FAA used in its 2013 PED policy reframing — operators (including Part 121 carriers) conducted aircraft-level testing and determined that consumer PEDs in passenger use do not cause interference. Most carriers now allow PED use gate-to-gate (with cellular service disabled where applicable).

Always-permitted devices (paragraph b)(1)-(4): Portable voice recorders, hearing aids, heart pacemakers, electric shavers, and any device the operator has determined as non-interfering. These are the categorical exceptions, set in 1960s-era regulatory language and never updated.

Part 91 IFR application: The reg applies to ANY aircraft operating under IFR, not just air carriers. A Part 91 IFR flight in a Cessna 172 is subject to § 91.21 just like an airliner. In practice, the pilot's own determination that the iPad EFB is non-interfering (under (b)(5)) is sufficient for Part 91 use — but the determination must be a real determination, not a default assumption.

Cellular service in flight: Note that § 91.21 is the FAA rule on PED use. Cellular phone use in flight is also restricted by the FCC under 47 CFR § 22.925, which prohibits airborne use of certain cellular frequencies regardless of the aircraft type or operating rule.

Reference: FAA Portable Electronic Devices ARC Final Report (2013); AC 91.21-1D (operator PED program guidance for Part 91/135 operators); FCC 47 CFR § 22.925.