Aeronautical Information Manual (AIM), page 238

Index   237 -- Page 238 -- 239

c. Pilots complying with speed adjustments 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
1. To aircraft operating between FL 280 and
10,000 feet, a speed not less than 250 knots or the
equivalent Mach number.

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

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

(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."
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

(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
The phraseology "comply with restrictions" 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
terminate a speed adjustment where speed restric-
tions are published on a charted procedure.
When instructed to "comply with speed restrictions" or to
"resume published speed," ATC anticipates pilots will
begin adjusting speed the minimum distance necessary
prior to a published speed restriction so as to cross the
waypoint/fix at the published speed. Once at the published
speed, ATC expects pilots will maintain the published
speed until additional adjustment is required to comply
with further published or ATC assigned speed restrictions

4-4-8 ATC Clearances and Aircraft Separation

Page 238 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   237 -- Page 238 -- 239