Section 5. Air Carrier Computer Interface Program


Apply the provisions of this section when coordinating and implementing the air carrier computer interface program. The term air carrier used in this section includes scheduled air taxi operators that have the capability to transmit flight plans via the NADIN/Center B interface to ARTCC computer programs.


The ARTCC, upon request from an air carrier to participate in this program, must:

  1. Obtain local contacts from the air carrier for coordinating the program.
  2. Provide the air carrier with a contact for the continued coordination of the program.
  3. Ensure that the air carrier is apprised of the criteria in paragraph 6-5-3, Criteria for Participation.

Air carriers participating in the program must be advised of the following criteria:

  1. Departure points and destinations must be contained within the CONUS. However, some users have made previous arrangements with various ICAO States (Puerto Rico, Panama, Canada, etc.) to accept domestic format. These agreements must be honored.
  2. Flight plans must not be filed more than 3 hours in advance of the proposed departure times. Flight plans must be telephoned to the appropriate facility if less than 45 minutes from the proposed departure time. All changes in the flight plan after filing must be telephoned to the appropriate facility.
  3. All flight plans must adhere to the format convention and content specified in paragraph 6-5-4, Format Conventions, and paragraph 6-5-5, Message Content.

Flight plans must be filed in the following format:

  1. Data input must adhere to a fixed order and not exceed the stated maximum number of characters or elements allowed for each field in messages addressed to an ARTCC computer.
  2. Each field of data is composed of one or more elements. Discrete elements of information within a field are separated by delimiters; generally, virgules (/) or periods.
  3. Some fields contain the necessary functions to operate the computer adapters and are designated by alpha characters. Do not separate these fields with spaces.
  4. One space character must be entered at the end of each data field, except:
  1. The first data field of a message must not be preceded by a space.
  2. The last data field of message need not be followed by a space.
  3. The Remarks (Field 11) terminate with the last nonspace character transmitted.

The complete message content, the order of data, the number of characters allowed within any data field or element, and any associated operational procedure or restrictions must be as follows: (See FIG 6-5-1).

  1. Start of Message Code (Field A). Appropriate individual company coding to ensure entry into the AFTN system.
  2. Preamble Line (Field B). Consists of priority and addressees in ICAO format.
  3. End of Line Function (Field C). Three characters composed of carriage return, carriage return, line feed.
  4. Computer Adapter Turn-on Code (Field D). Three characters specifying the facility adapter code plus carriage return, carriage return, line feed.
  5. Source Identification (Field 00). Ten characters followed by a space character in the following order:
  1. Three-character address of the originating office.
  2. Four-character (digits) time in UTC.
  3. Three characters (digits) representing the number of the message being transmitted to the specific facility. All facilities will have individual sequence numbers beginning with number 000 at 0000Z.
  1. Message Type (Field 01). The letters “FP” followed by a space character.
  2. Aircraft Identification (Field 02). Consists of two to seven characters followed by a space character. The first character of the identification must be a letter.
  3. Aircraft Data (Field 03). Consists of two to nine characters followed by a space character. Aircraft data within the field may vary from one to three elements consisting of:
  1. Super or heavy aircraft indicator (H/): When aircraft are designated super or heavy, the heavy indicator is mandatory.
  2. Type of Aircraft: This element is mandatory and contains the standard aircraft type designator, in accordance with FAA Order JO 7360.1, Aircraft Type Designators.
  3. Equipment Suffix: This element is optional and consists of a slash followed by one letter which is one of the approved designators identifying transponder and/or navigation equipment.
  1. Airspeed (Field 05): Consists of two to four characters followed by a space character. This field must include the filed true airspeed in knots or Mach speed.
  2. Departure Point (Field 06): The airport of departure must be two to a maximum of five characters using the authorized identifier as listed in FAA Order JO 7350.9, Location Identifiers, and must duplicate the first element of the route of flight (Field 10).
  3. Proposed Departure Time (Field 07): Consists of five characters followed by a space character. This field contains the letter “P” followed by a four-digit time group (in UTC).
  4. Requested Altitude (Field 09): Consists of two to three characters followed by a space character. Altitudes or flight levels, as appropriate, must be expressed in hundreds of feet.
  5. Route of Flight (Field 10): The route of flight consists of the departure point, the route of flight, and a destination:
  1. Field 10 is fixed sequence field and must begin with a fix; e.g., fix.route.fix.route., etc. An element is separated from another element by a period character.
  2. When consecutive fix elements or route elements are filed, the fixed sequence format is maintained by inserting two period characters between the filed Field 10 elements; e.g., fix..fix or route..route.
  3. The maximum number of filed field elements for computer-addressed flight plans is 40. Double period insertions do not count against the 40-element limitation.
  1. Fix Descriptions: A fix identifies a geographic point and must be one of either domestic, Canadian, or international identifiers, which are two to twelve alphanumeric characters.
  2. Route Descriptions: A route element must be one of the following:
  1. Airway: The official airway designator must be filed.
  2. Standard Instrument Departures (SID): SIDs, if used, must be filed by the computer-code designator as the second element of Field 10 and followed by the transition fix.
  3. Standard Terminal Arrivals (STAR): STARs, if used, must be filed by the computer-code designator as the next to last element of Field 10 and be immediately preceded by the entry or transition fix.
  4. Published Radials: Published radials; e.g., within a preferred route, are considered airways. Do not file unpublished radials.



  1. North American Routes (NAR): Numerically coded routes preplanned over existing airways and route system to and from specific coastal fixes serving the North Atlantic.



  1. Estimated Time En Route Suffix: Consists of an element separator (/) and four digits appended to the destination. Leading zeros are required, and the time en route is expressed in hours and minutes.



  1. Remarks (Field 11): Consists of the remarks code character--a clear sky symbol or an overcast sky symbol, and the remarks.


If remarks (Field 11) are present, a space is required after the last element of Field 10. If remarks are not present, no space is required, and Field E (End of Text) should be the next entry.

  1. The overcast sky symbol limits the transmittal of the remarks to the center controlling a point of departure. This should be used when the only remarks are a request for a full route clearance (FRC). It may also be used when it is known that the remarks are only pertinent to the center controlling the departure airport.
  2. Remarks are not interpreted by the NAS En Route Program and are optional. When used, they must be limited to flight information pertinent to ATC.
  1. End of Text Signal/End of Message Function (Field E).


Fields 04 and 08 are not applicable to proposed flight plans and have been intentionally omitted. (See FIG 6-5-1.)

FIG 6-5-1

Automated Flight Plan Message

A graphic depicting a completed automated flight message plan.

Computer Flight Data Input Chart






Start of Message (SOM code)


Required for SOM recognition


Priority/Address Line


Provides priority and addressee




Identifies time of transmission and originator


End of Line (EOL) Function

New Line Key

Required to end all lines except line of text



Enter Key

Terminates message