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AIM

10/12/17

4

−4−2

ATC Clearances and Aircraft Separation

or route different from that requested by the pilot. In
addition, flow patterns have been established in
certain congested areas or between congested areas
whereby traffic capacity is increased by routing all
traffic on preferred routes. Information on these flow
patterns is available in offices where preflight
briefing is furnished or where flight plans are
accepted.

2.

When required, air traffic clearances include

data to assist pilots in identifying radio reporting
points. It is the responsibility of pilots to notify ATC
immediately if their radio equipment cannot receive
the type of signals they must utilize to comply with
their clearance.

d. Altitude Data.

1.

The altitude or flight level instructions in an

ATC clearance normally require that a pilot
“MAINTAIN” the altitude or flight level at which the
flight will operate when in controlled airspace.
Altitude or flight level changes while en route should
be requested prior to the time the change is desired.

2.

When possible, if the altitude assigned is

different from the altitude requested by the pilot, ATC
will inform the pilot when to expect climb or descent
clearance or to request altitude change from another
facility. If this has not been received prior to crossing
the boundary of the ATC facility’s area and
assignment at a different altitude is still desired, the
pilot should reinitiate the request with the next
facility.

3.

The term “cruise” may be used instead of

“MAINTAIN” to assign a block of airspace to a pilot
from the minimum IFR altitude up to and including
the altitude specified in the cruise clearance. The pilot
may level off at any intermediate altitude within this
block of airspace. Climb/descent within the block is
to be made at the discretion of the pilot. However,
once the pilot starts descent and verbally reports
leaving an altitude in the block, the pilot may not
return to that altitude without additional ATC
clearance.

REFERENCE

Pilot/Controller Glossary Term

− Cruise.

e. Holding Instructions.

1.

Whenever an aircraft has been cleared to a fix

other than the destination airport and delay is
expected, it is the responsibility of the ATC controller
to issue complete holding instructions (unless the

pattern is charted), an EFC time, and a best estimate
of any additional en route/terminal delay.

2.

If the holding pattern is charted and the

controller doesn’t issue complete holding instruc-
tions, the pilot is expected to hold as depicted on the
appropriate chart. When the pattern is charted, the
controller may omit all holding instructions except
the charted holding direction and the statement
AS PUBLISHED

, e.g., “HOLD EAST AS

PUBLISHED.”

 Controllers must always issue

complete holding instructions when pilots request
them.

NOTE

Only those holding patterns depicted on U.S. government
or commercially produced charts which meet FAA
requirements should be used.

3.

If no holding pattern is charted and holding

instructions have not been issued, the pilot should ask
ATC for holding instructions prior to reaching the fix.
This procedure will eliminate the possibility of an
aircraft entering a holding pattern other than that
desired by ATC. If unable to obtain holding
instructions prior to reaching the fix (due to
frequency congestion, stuck microphone, etc.), hold
in a standard pattern on the course on which you
approached the fix and request further clearance as
soon as possible. In this event, the altitude/flight level
of the aircraft at the clearance limit will be protected
so that separation will be provided as required.

4.

When an aircraft is 3 minutes or less from a

clearance limit and a clearance beyond the fix has not
been received, the pilot is expected to start a speed
reduction so that the aircraft will cross the fix,
initially, at or below the maximum holding airspeed.

5.

When no delay is expected, the controller

should issue a clearance beyond the fix as soon as
possible and, whenever possible, at least 5 minutes
before the aircraft reaches the clearance limit.

6.

Pilots should report to ATC the time and

altitude/flight level at which the aircraft reaches the
clearance limit and report leaving the clearance limit.

NOTE

In the event of two

−way communications failure, pilots are

required to comply with 14 CFR Section 91.185.

4

−4−4. Amended Clearances

a.

Amendments to the initial clearance will be

issued at any time an air traffic controller deems such