When does the sterile cockpit start?

The concept originated in the United States. In 1981 the FAA added rule 14 CFR 121.542, the sterile cockpit rule, to the airline regulations: during critical phases of flight, pilots may not engage in activities unrelated to the safe operation of the aircraft, such as non-urgent paperwork, meals, or non-operational conversation. The rule defines those phases as taxiing, takeoff, landing, and any flight below 10,000 ft (3,050 m), except cruise. The sterile cockpit therefore begins when the aircraft starts moving under its own power on the ground, and during descent it kicks back in when crossing 10,000 ft.

Europe adopted an equivalent rule in EASA's Air OPS regulations (CAT.GEN.MPA.124, applicable since 2015), which requires operators to define sterile cockpit procedures in their manuals; most copy the 10,000 ft threshold, and some raise it at high-altitude airports.

The rule was written after a series of accidents in which pilots, distracted by conversation unrelated to the flight, lost situational awareness. The reference case was Eastern Air Lines Flight 212, a DC-9 that crashed on approach to Charlotte in September 1974 while the crew was talking about politics and used cars; the NTSB cited the conversation as a contributing factor.

Cabin crew are notified by an agreed-upon signal, often a cycling of the seatbelt sign or an interphone call, and from that moment the cabin crew does not contact the pilots except for an emergency or a safety-related matter: smoke, fire, a passenger tampering with an exit. Once the threshold is passed during climb, another signal indicates that communication has returned to normal.