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AIM 

6/17/21 

assigns a new speed, issues a vector, assigns a direct 
route, or issues an approach clearance. 

b. 

ATC will express all speed adjustments in 

terms of knots based on indicated airspeed (IAS) in 
5 or 10 knot increments except that at or above FL 
240 speeds may be expressed in terms of Mach 
numbers in 0.01 increments. The use of Mach 
numbers is restricted to turbojet aircraft with Mach 
meters. 

c. 

Pilots complying with speed adjustments 

(published or assigned) are expected to maintain a 
speed within plus or minus 10 knots or 0.02 Mach 
number of the specified speed. 

d. 

When ATC assigns speed adjustments, it will 

be in accordance with the following recommended 
minimums: 

1. 

To aircraft operating between FL 280 and 

10,000 feet, a speed not less than 250 knots or the 
equivalent Mach number. 

NOTE

 

1. 

On a standard day the Mach numbers equivalent to 

250 knots CAS (subject to minor variations) are: 
FL 240

0.6 

FL 250

0.61 

FL 260

0.62 

FL 270

0.64 

FL 280

0.65 

FL 290

0.66. 

2. 

When an operational advantage will be realized, speeds 

lower than the recommended minima may be applied. 

2. 

To arriving turbojet aircraft operating below 

10,000 feet: 

(a) 

A speed not less than 210 knots, except; 

(b) 

Within 20 flying miles of the airport of 

intended landing, a speed not less than 170 knots. 

3. 

To arriving reciprocating engine or turboprop 

aircraft within 20 flying miles of the runway 
threshold of the airport of intended landing, a speed 
not less than 150 knots. 

4. 

To departing aircraft: 

(a) 

Turbojet aircraft, a speed not less than 

230 knots. 

(b) 

Reciprocating engine aircraft, a speed not 

less than 150 knots. 

e. 

When ATC combines a speed adjustment with 

a descent clearance, the sequence of delivery, with the 
word “then” between, indicates the expected order of 
execution. 

EXAMPLE

 

1. 

Descend and maintain (altitude); then, reduce speed to 

(speed). 

2. 

Reduce speed to (speed); then, descend and maintain 

(altitude). 

NOTE

 

The maximum speeds below 10,000 feet as established in 
14 CFR Section 91.117 still apply. If there is any doubt 
concerning the manner in which such a clearance is to be 
executed, request clarification from ATC. 

f. 

If ATC determines (before an approach 

clearance is issued) that it is no longer necessary to 
apply speed adjustment procedures, they will: 

1. 

Advise the pilot to “resume normal speed.” 

Normal speed is used to terminate ATC assigned 
speed adjustments on segments where no published 
speed restrictions apply. It does not cancel published 
restrictions on upcoming procedures. This does not 
relieve the pilot of those speed restrictions which are 
applicable to 14 CFR Section 91.117. 

EXAMPLE

 

(An aircraft is flying a SID with no published speed 
restrictions. ATC issues a speed adjustment and instructs 
the aircraft where the adjustment ends): “Maintain two two 
zero knots until BALTR then resume normal speed.” 

NOTE

 

The ATC assigned speed assignment of two two zero knots 
would apply until BALTR. The aircraft would then resume 
a normal operating speed while remaining in compliance 
with 14 CFR Section 91.117. 

2. 

Instruct pilots to “comply with speed 

restrictions” when the aircraft is joining or resuming 
a charted procedure or route with published speed 
restrictions. 

EXAMPLE

 

(ATC vectors an aircraft off of a SID to rejoin the procedure 
at a subsequent waypoint. When instructing the aircraft to 
resume the procedure, ATC also wants the aircraft to 
comply with the published procedure speed restrictions): 
“Resume the SALTY ONE departure. Comply with speed 
restrictions.” 

CAUTION

 

The phraseology “Descend via/Climb via SID” requires 
compliance with all altitude and/or speed restrictions 
depicted on the procedure. 

3. 

Instruct the pilot to “resume published 

speed.” Resume published speed is issued to 

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ATC Clearances and Aircraft Separation