U.S. Department 

of Transportation 

Federal Aviation 

Administration

Advisory 

Circular

Subject: INTERNATIONAL CIVIL 

AVIATION ORGANIZATION THREELETTER DESIGNATOR AND 

TELEPHONY DESIGNATOR

1. PURPOSE. 

Advisory Circular 120-26J defines the criteria 

and procedures for obtaining an International 

Civil Aviation Organization (ICAO) threeletter and/or telephony designator assignment. 

2. CANCELLATION. 

Advisory Circular No. 120-26H, dated 

6/21/91, is canceled. 

3. EXPLANATION OF CHANGES.

 a. All references to the Federal Aviation 

Administration (FAA), Airspace-Rules and 

Aeronautical Information Division, Air Traffic 

Publications Branch (ATP-210), have been 

changed to FAA Headquarters. FAA 

Headquarters, Flight Services Division is 

referred to as ATP-300. Air Traffic Planning 

and Procedures Service is referred to as ATP. 

Effective 1/1/05, all of the references above 

are changed to Headquarters, Flight Services 

Safety and Operations Support. 

 b. Editorial and grammatical changes have 

been made to improve the clarity of this 

advisory circular. 

 c. All references to radiotelephony have 

been changed to telephony, as radiotelephone 

operator licenses are no longer required. 

 d. ICAO will not approve telephonies that 

Date: 1/1/05 AC No: 120-26J 

Initiated by: OPERATIONAL 

PROCEDURES

are either numbers or letters. (Par.6.b) 

 e. The round trip and minimum aircraft 

requirements for a three-letter and/or 

telephony designator have been modified. (Par. 

6c) 

 f. In accordance with Presidential 

Proclamation 5928, United States domestic 

airspace extends to 12 nautical miles from the 

coast of the United States (U.S.). 

 g. Regional Air Traffic Division (ATD) 

responsibilities have been redefined (Par.14), 

and redesignated as Service Area Directors. 

4. RELATED READING MATERIAL. 

Additional information on three-letter 

telephony, local telephony and special 

telephony designators, may be found in FAA 

Order 7340.1, Contractions; FAA Order 

7210.3, Facility Operation and Administration; 

FAA Order 7110.65, Air Traffic Control; Title 

47 of the Code of Federal Regulation (CFR), 

section 87.107; and ICAO Document 8585, 

Designators for Aircraft Operating Agencies, 

Aeronautical Authorities, and Services.

5. DEFINITIONS.

 a. Three-Letter Designator – A threeletter designator is used in conjunction with 

the flight number and serves as the aircraft 

identification in the air traffic control system. 
The authorized designator and flight/trip 

number are used for company business in lieu 

of the aircraft registration number. 

b. Telephony Designator – (CALLSIGN) 

Normally the aircraft operating company 

and/or servicing agency name or a 

pronounceable abbreviation of the name is 

used in combination with the flight number. 

The telephony designator is normally assigned 

simultaneously with the three-letter designator 

and becomes the aircraft identification for all 

voice communications with air traffic control 

facilities and operating services. 

6. CRITERIA.

 a. A three-letter designator is registered 

with the FAA for aircraft operating agencies 

and companies that, in the opinion of the State 

of jurisdiction (U.S.), require a specific threeletter designator. Three-letter designators are 

assigned by ICAO on a worldwide basis to an 

aircraft operating or servicing company 

conducting commercial domestic and/or 

international operations. ICAO three-letter 

designators may be used on the international 

telecommunications service when deemed 

advantageous for air traffic control and 

operational purposes. 

 b. A telephony designator is approved by 

ICAO and should be pronounceable and 

suitable phonetically in at least one of the 

following languages: English, French, or 

Spanish. The telephony designator, consisting 

of not more than two words and three 

syllables, should preferably resemble the name 

of the aircraft company, operating authority, or 

servicing organization. This reduces the 

amount of verbiage created on-line, 

contributing to similar sounding telephony 

designator confusion. Letters and numbers are 

not assigned as telephony designators.

However, companies that have previously been 

assigned letters and numbers as telephony 

designators will retain those telephony 

designators.

 c. The award of a three-letter designator 

and telephony designator is for the 

improvement of Air Traffic Control (ATC) 

communications, and the reduction of 

frequency congestion. The requestor should 

show that award would have a significant 

impact on the ATC system (defined as 

affecting three or more aircraft). A three-letter 

designator or telephony designator may be 

awarded to; (1) an aircraft operating company 

and/or servicing agency that operate or service 

15 or more scheduled non-seasonal 

international round trip air operations per 

week, and generate appropriate flight 

movement messages over the National 

Aviation Data Inter-change Network 

(NADIN); or, (2) at least 20 scheduled nonseasonal domestic commercial round trip air 

operations per week. Aircraft operating 

companies and/or servicing agencies, that do 

not demonstrate minimum criteria, may apply 

for a waiver of these criteria with 

Headquarters, Flight Services Safety and 

Operations Support, and still be awarded a 

three-letter designator or telephony designator. 

The waiver must be deemed advantageous to 

the U.S. Air Traffic Control (ATC) system and 

operationally appropriate by the FAA. Waivers 

are authorized on an individual basis. 

 d. ICAO Document 8585 states that the 

three-letter designator of an entity may be used 

as part of the address indication for the 

Aeronautical Fixed Telecommunications 

Network (AFTN). Aircraft operating 

companies and/or servicing agencies desiring 

to send and/or receive communications via 

AFTN, must complete a Memorandum of 

Agreement on usage, prior to being allowed to 

connect to NADIN for international and 
domestic telecommunications services. 

NADIN is an integrated worldwide system of 

aeronautical fixed circuits (including AFTN) 

providing exchange of messages between 

aeronautical fixed stations within the network. 

NADIN telecommunication service provides 

an electronic media for transmission of 

international flight movement messages and 

flight plans.

 e. NADIN connections are authorized for 

aircraft operators and/or servicing agencies to 

introduce aircraft movement data into the air 

navigation system, and for the exchange of 

permissible information, in accordance with 

ICAO Annex 10, and Title 19 of 14 CFR, Part 

189. 

 f. NADIN authorized users must have a 

Memorandum of Agreement (MOA) with the 

FAA to access the NADIN, and for 

transmitting non-ICAO (domestic) flight 

movement messages. The use of the assigned 

designator will not be approved until the MOA 

has been finalized. For additional information 

concerning MOA's, contact Headquarters, 

Flight Services Safety and Operations Support.

.

 g. Companies that pay a service-fee 

company to input data, must assure that the 

service-fee company has a MOA on file with 

the FAA. Those companies that will input 

data solely through FAA facilities must state in 

their request that the company does not require 

a NADIN connection, they have not hired a 

service fee company for data entry, and that 

they will be responsible for entering all data 

through FAA facilities. 

 

7. PROCEDURES FOR APPLICATION. 

Requests for ICAO three-letter designator 

and/or telephony designators should be 

addressed to the Service Area Directors, at the 

appropriate FAA Service Area Office. The 

regional office will approve, deny, or request 

information from the applicant/requestor. The 

regional office will then forward an acceptance 

recommendation, to Headquarters, Flight 

Services Safety and Operations Support. 

 b. The Service Area Director will ensure all 

documentation submitted by the applicant is 

validated before data is forwarded. It is the 

Service Area’s responsibility to review the 

application and determine if the applicant 

meets the Headquarters, Flight Services Safety 

and Operations Support, ICAO and AC120-26 

criteria, before submitting recommendations to 

Headquarters. Upon that determination, the 

request is either denied by the region or 

submitted to FAA Headquarters, Operational 

Procedures, with recommendations supporting 

the approval. 

 c. Three-letter and telephony designators 

are assigned by Headquarters, Flight Services 

Safety and Operations Support, with approval 

of ICAO. Assignments are made on a 

worldwide basis, for commercial 

domestic/international air traffic control 

operations, and use in the NADIN system. 

When ICAO officially approves the 

application, it will be returned to the region. 

The Service Area Director will notify its ATC 

facilities, and Headquarters, Flight Services 

Safety and Operations Support, will notify the 

other facilities and assure publication in FAA 

Order 7340.1, Contractions. 

8. DOCUMENTATION. 

To determine eligibility for an ICAO threeletter and/or telephony designator, the 

following information is necessary: 

 a. Name and address of the company, 

contact personnel and telephone numbers. 

 b. The number and type of aircraft 

operation or service provided. (minimum 3 

aircraft; a list of operators served is required 

for servicing operations.)
 c. The method of data entry into the 

NADIN system. (Is NADIN connection 

needed by applicant? Was a service fee 

company hired? Is applicant filing through 

FAA facilities?) 

 d. The number and type of NADIN 

messages generated on a daily basis, if 

connected. 

 e. A copy of the company/operator flight 

schedule. 

 Not required for servicing agencies.

 f. A copy of the FAA Certificate that 

authorizes the company operations, stating the 

Title 14 CFR Part under which operations are 

to be conducted, i.e., 14 CFR Parts 121, 125 

and 135. 

NOTE: Company operations under

Title 14 CFR, Part 91 solely, do not make a 

company eligible for an ICAO three-letter 

and/or telephony designator (s).

 g. Provide at least five (5) suggested 

three-letter designators and telephony 

designators, in order desired. 

NOTE: The required administrative

period for approval of a company threeletter and/or telephony designator is 

approximately 90 calendar days. Failure to 

submit proper documentation may delay 

designator assignment

9. BASIS FOR ASSIGNMENT. 

 a. ICAO approved three-letter and/or 

telephony designator assignments are

supported by the FAA, if deemed

advantageous to the U.S. Air Traffic Control 

(ATC) system. 

 b. Approved ICAO three-letter designator 

be included in the remarks section of flight 

or telephony designators will not be assigned 

to eliminate problems resolvable by changing 

registration numbers, or similar sounding 

company names. 

c. Title 14 CFR 91.169 (d) requires when 

a flight plan has been activated, the pilot in 

command shall notify a Flight Service Station 

or ATC facility upon canceling or completing 

the flight under the flight plan. This will avoid 

the FAA implementing search and rescue 

procedures.

10. CHANGES IN COMPANY STATUS. 

Headquarters, Flight Services Safety and 

Operations Support, should be notified in 

writing immediately, when an assigned threeletter and/or telephony designator is no longer 

required, or upon a change in the name, 

address, or physical location of the company. 

Any designator released will not be reassigned 

for at least 60 calendar days. Exceptions will 

be considered on an individual basis. Listed 

below are some reasons for the notification of 

release: 

 a. Operations are permanently suspended 

or canceled for any reason; or, 

b. Company names holding more than one 

three-letter and/or telephony designator. 

11. USE OF AIRCRAFT COMPANY 

THREE-LETTER AND/OR TELEPHONY 

DESIGNATOR. 

 a. Authorized three-letter designators 

and/or telephony designators are valid when 

aircraft are flown according to provisions of 

the CFR under which an operating certificate 

was obtained from the FAA. 

 b. A new or changed three-letter 

designator and/or telephony designator should 

(1) commemorative flights; 
plans for at least 60 days following the 

effective date. 

 c. Headquarters, Flight Services Safety and 

Operations Support, reserves the right to revise 

or cancel any three-letter and/or telephony 

designator assignment, should confusion result 

within the United States. ICAO Document 

8585 states in the interest of safety, simple 

procedures should be developed and 

maintained by states and aircraft operating 

companies/agencies for detecting, reporting 

and eliminating similar sounding 

radiotelephonies that may cause confusion or 

mistakes in identification.

12. PUBLICATION OF AIRCRAFT 

COMPANY THREE-LETTER 

DESIGNATORS AND/OR TELEPHONY 

DESIGNATORS. 

Effective dates of aircraft company three-letter 

and/or telephony designators will be timely to 

permit entry into FAA Order 7340.1, 

Contractions, and the Stored Flight Plan 

Program. Affected FAA facilities will be 

advised of the authorized three-letter 

designator and/or telephony designator 

pending publication in appropriate FAA and 

ICAO documents 

13. SPECIAL TELEPHONY 

DESIGNATOR ASSIGNMENTS. 

 a. Special telephony designators may be 

temporarily authorized only when their 

assignment will identify special handling 

required by air traffic control. 

b. Special telephony designators are 

approved by the FAA. 

 c. Special telephony designators may be 

authorized for the following categories: 

plans. 

 (2) large number of aircraft participating 

in an organized race; 

 (3) aircraft operating during an 

emergency or disaster condition; or, 

 (4) aircraft requiring special handling for 

test purposes. 

 d. Requests should be made to 

Headquarters, Flight Services Safety and 

Operations Support, and include the following: 

 (1) type of flight; 

 (2) handling required; 

 (3) type and number of aircraft; and 

 (4) routes and duration of operation. 

14. LOCAL TELEPHONY DESIGNATOR 

ASSIGNMENTS

 a. The Service Area Director issues local 

telephony designators, according to FAA 

Order 7210.3, Facility Operation and 

Administration.

 b. Local telephony designators are used 

only for communications with local airport 

traffic control towers and/or air traffic facilities 

for VFR (VMC) operations. A Letter Of 

Agreement (LOA) is required between the 

local tower/facility and the requesting 

company/applicant. The LOA will contain 

provisions to ensure that local telephony is 

used only with facilities that are signatories to 

the agreement. 

 c. When a LOA expires, the local 

tower/facility will notify the company/ 

applicant for renewal. Local telephony 

designators are not to be used for filing flight 
 d. The Service Area Directors shall 

coordinate with bordering Service Areas, to 

assure that telephonies do not overlap. The 

Service Area Directors shall maintain a 

regional master database for local telephony. 

 e. The Service Area Directors shall 

forward copies of all approved telephonies to 

Headquarters, Flight Services Safety and 

Operations Support, for inclusion in the 

national database.

Paul J. Sheridan 

Acting Director, Flight Services Safety 

 and Operations Support
DO NOT PRINT OR INCLUDE THIS INFORMATION IN THE PUBLICATION 

file: n:\320.1\idents\ac\120-26J\120-26J3E .doc 

spellchecked after amendment 5/7/03, 5/19/04 & 7/8/04 ET 

removed references to ATP-320 

Changed font to 12, per Sharon Kline 11/19/04, margined and spellchecked ET