Format:

b
c

OPEN BRACKET
(a) Message Type Designator 3 LETTERS as follows:
ALR RCF  Alerting Radio communication failure 
FPL CHG CNL DLA DEP ARR  Filed flight plan Modification Cancellation Delay Departure Arrival 
CPL EST CDN ACP LAM  Current flight plan Estimate Co-ordination Acceptance Logical acknowledgement 
RQP RQS SPL  Request flight plan Request supplementary flight plan Supplementary flight plan 

Previous  Next type 
type of  This type  of field 
field or  of field  or 
symbol  is used in  symbol 
( (  ALR RCF  5 7 
(  FPL  7 
(  CHG  7 
(  CNL  7 
(  DLA  7 
(  DEP  7 
(  ARR  7 
(  CPL  7 
(  EST  7 
(  CDN  7 
(  ACP  7 
(  LAM  ) 
( ( (  RQP RQS SPL  7 7 7 

*  Unless instructed otherwise, this field shall contain only the single element (a). Elements (b) or (b) and (c) are for use when messages are generated by, and/or exchanged between, the computer systems of ATS units.
(b)  Message Number 1 to 4 LETTER(S) identifying the sending ATS unit, followed by OBLIQUE STROKE (/) followed by 1 to 4 LETTER(S) identifying the receiving ATS unit, followed by 3 DECIMAL NUMERICS giving the serial number of this message in the
sequence of messages transmitted by this unit to the indicated receiving ATS unit.
Field Type 3 (cont.)
(c) Reference Data
1 to 4 LETTER(S) followed by OBLIQUE STROKE (/) followed by 1 to 4 LETTER(S) followed by 3 DECIMAL NUMERICS, giving the “message number” contained in element (b) of the operational message which began the sequence of messages of which this message is a part.
Examples:  (FPL (CNL (CHGA/B234A/B231 (CPLA/B002
Field Type 5 — Description of Emergency
FIELD TYPE 5

Format: –

c
a /
/

SINGLE HYPHEN
(a)  Phase of Emergency 
or or  INCERFA if an uncertainty phase, ALERFA if an alert phase, DETRESFA if a distress phase 
has been declared in respect of the aircraft concerned. 

Previous  Next type 
type of  This type  of field 
field or  of field  or 
symbol  is used in  symbol 
3  ALR  7 

OBLIQUE STROKE
(b) Originator of Message
8 LETTERS, being the 4-letter ICAO location indicator plus the 3-letter designator of the ATS unit originating the message followed by the letter X or, if applicable, the one-letter designator identifying the division of the ATS unit originating the message.
OBLIQUE STROKE
(c) Nature of Emergency
SHORT PLAIN LANGUAGE TEXT, as necessary to explain the nature of the emergency, with natural spaces between the words.
Example: –ALERFA/EINNZQZX/REPORT OVERDUE
Field Type 7 — Aircraft Identification and Mode A Code
FIELD TYPE 7
*
(a) Max. 7 characters

Format: –
/

SINGLE HYPHEN

(a) Aircraft Identification
NOT MORE THAN 7 CHARACTERS, being the aircraft identification shown in the filed flight plan and composed as specified in Appendix 2, Section 2.
*  This field may be terminated here in messages relating to flights operating within areas where SSR is not used, or when the SSR Code information is not known or would not be meaningful to the accepting unit.
OBLIQUE STROKE
(b) SSR Mode
LETTER A giving the SSR Mode related to (c).
　
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