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The Pilots Desk
US-FAA14 CFR 121.303

Airplane instruments and equipment

Read the official rule

This regulation establishes the baseline instrument and equipment requirements for Part 121 air carrier operations. It mandates that all required instruments and equipment must be properly approved and installed according to airworthiness standards.

Key practical requirements include:

  • All airspeed indicators must display knots (not mph), and all airspeed limitations in the Flight Manual and placards must also be in knots
  • Before takeoff, the aircraft must have operable instruments and equipment required by its type certificate, airworthiness regulations, and the specific sections referenced (121.305-121.359, etc.)
  • Different equipment lists apply depending on the type of operation being conducted

The regulation essentially creates a comprehensive equipment checklist by referencing numerous other sections. Aircraft cannot legally depart unless all applicable required equipment is working, except where specific minimum equipment list (MEL) provisions in §§121.627-121.628 allow certain inoperative items. This ensures standardization and safety across all Part 121 operations.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*

This is an original plain-English explanation for training and reference, not legal advice and not for navigation. Always rely on the current official rule linked above. Last reviewed June 20, 2026.