Definition
A federal regulation in Title 14 of the Code of Federal Regulations, part 121, section 121.542, that establishes the Sterile Flight Deck Rule. It prohibits flight crewmembers from performing any non-essential duties or activities during critical phases of flight, and prohibits non-essential conversation between crewmembers and between crew and cabin personnel during those phases. Critical phases of flight are defined as all ground operations involving taxi, takeoff, landing, and all other flight operations conducted below 10,000 feet, except cruise flight.
Plain English
This is the FAA rule that says pilots must focus only on flying the aircraft during the busiest and most dangerous parts of a flight. No chatting, no paperwork that can wait, no distractions -- just flying. It applies during taxi, takeoff, landing, and any flight below 10,000 feet that isn't cruising.
Context Anchor
Seen in discussions of sterile flight deck procedures, crew resource management, and instructor guidance about avoiding distractions during high-workload phases of flight.
Derivation
CFR' stands for Code of Federal Regulations -- the published rulebook of U.S. federal agencies. Title 14 covers Aeronautics and Space. Part 121 covers scheduled airline operations. The numbering system lets pilots and inspectors point to a specific rule precisely.
Why Pilots Care
Following this rule reduces distraction-related errors and helps pilots maintain full attention on aircraft control and decision-making when workload is highest.
Analogy
It is like a quiet rule in the cockpit during the parts of flight where timing and attention matter most. The crew can still say anything needed for safety, but unrelated talk waits until the workload drops.
Intuition Check
Do not read this as just a reference number with no practical effect. It points to a required operating rule: during critical phases of flight, flight crews must keep attention on safe aircraft operation.
Example Sentence 1
Once cleared to taxi, the captain reminded the first officer that they were now under the sterile flight deck rule of 14 CFR part 121, section 121.542.
Example Sentence 2
During recurrent training, the instructor used 14 CFR part 121, section 121.542 to illustrate how a sterile cockpit prevents the kinds of distractions that have caused past accidents.