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AIM 

6/17/21 

TBL 5

3

Crossing Constraint Message Elements (CSTU) 

CPDLC Message Sets 

Operational Definition in PANS

ATM (Doc 4444) 

FANS 1/A 

ATN B1 

Response 

Message 
Element 

Identifier 

Message Element 

Intended Use 

Format for 

Message Element 

Display 

UM49 CROSS (

posi-

tion

) AT AND MAIN-

TAIN (

altitude

Note 1. 

 A vertical 

range cannot be pro-
vided. 
Note 2. 

 This mes-

sage element is equiv-
alent to CSTU

1 plus 

LVLU

5 in Doc 4444. 

N/A 

W/U 

CSTU

Instruction that the 
specified position 
is to be crossed at 
the specified level 
or within the speci-
fied vertical range. 

CROSS 

(position) 

AT 

(level) 

UM61 CROSS 

(posi-

tion) 

AT AND MAIN-

TAIN 

(altitude)

 AT 

(speed) 
Note 1. 

 A vertical 

range cannot be pro-
vided. 
Note 2. 

 This mes-

sage element is equiv-
alent to CSTU

14 plus 

LVLU

5 in Doc 4444. 

UM61 CROSS 

(position) 

AT AND 

MAINTAIN 

(level) 

AT 

(speed) 

W/U 

CSTU

14 

Instruction that the 
specified position 
is to be crossed at 
the level or within 
the vertical range, 
as specified, and at 
the specified 
speed. 

CROSS 

(position) 

AT 

(level)

 AT 

(speed) 

TBL 5

3

Air Traffic Advisory Uplink Message Elements 

CPDLC Message Sets 

Operational Definition in PANS

ATM (Doc 4444) 

FANS 1/A 

ATN B1 

Response 

Message 
Element 

Identifier 

Message Element 

Intended Use 

Format for 

Message Element 

Display 

UM154 RADAR 
SERVICES TERMI-
NATED 

N/A 

ADVU

Advisory that the 
ATS surveillance 
service is terminat-
ed. 

SURVEILLANCE 
SERVICE TERMI-
NATED 

En Route Procedures 

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