Chapter 3. ICAO Aircraft Company Three-Letter Identifier and/or Telephony Designator Assignments and U.S. Special Telephony/Call Signs ▶ Section 1. Aircraft Company/Telephony/Three-Letter Designator Encode 3-1-1. Aircraft Company/Telephony/Three-Letter Designator Encode ▶ Section 2. Telephony/Aircraft Company/Three-Letter Designator Decode 3-2-1. Telephony/Aircraft Company/Three-Letter Designator Decode ▶ Section 3. Three-Letter Designator/Aircraft Company/Telephony Decode 3-3-1. Three-Letter Designator/Aircraft Company/Telephony Decode ▶ Section 4. U.S. Special Telephony/Call Signs 3-4-1. U.S. Special Telephony/Call Signs