Definition
A federal aviation regulation, found in Title 14 of the Code of Federal Regulations, Part 121, Section 121.542, that establishes the 'sterile cockpit rule' for air carrier operations. It prohibits flight crewmembers from performing any non-essential duties or activities during critical phases of flight — generally taxi, takeoff, landing, and all other flight operations conducted below 10,000 feet, except cruise flight. Non-essential activities include eating meals, engaging in non-essential conversation, and reading publications not related to the safe operation of the aircraft.
Plain English
This is the rule that says airline pilots must focus only on flying the airplane during the busiest and most dangerous parts of a flight. No chatting about non-flying topics, no meals, no distractions — just flying — whenever they're below 10,000 feet (other than in cruise) or during taxi, takeoff, and landing.
Context Anchor
Seen in discussions of runway incursions, taxi operations, crew discipline, and sterile cockpit procedures.
Derivation
14 CFR' means Title 14 of the Code of Federal Regulations — the volume of federal rules covering aeronautics and space. 'Part 121' covers scheduled airline operations. The '§' symbol means 'section.' So '14 CFR Part 121, § 121.542' is simply a precise address pointing to one specific rule within the airline regulations.
Why Pilots Care
Following this rule keeps the cockpit free of distractions during the exact moments when runway incursions are most likely to occur.
Intuition Check
Do not read this as just a random legal reference. In runway-incursion discussions, it points specifically to the rule that keeps cockpit activity focused during high-risk phases of flight.
Example Sentence 1
Under § 121.542, the first officer reminded the captain that they shouldn't discuss the layover hotel until they climbed through 10,000 feet.
Example Sentence 2
After a near-incursion the crew reviewed their compliance with 14 CFR Part 121, § 121.542 to identify any unnecessary conversation that may have contributed.