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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