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when leveling off at 10,000 feet MSL on descent, or
2,500 feet above airport elevation (prior to entering a
Class C or Class D surface area), when required for
speed reduction.
REFERENCE-
14 CFR Section 91.117.
NOTELeveling
off at 10,000 feet MSL on descent or 2,500 feet
above airport elevation (prior to entering a ClassC or
Class D surface area) to comply with 14 CFR
Section91.117 airspeed restrictions is commonplace.
Controllers anticipate this action and plan accordingly.
Leveling off at any other time on climb or descent may
seriously affect air traffic handling by ATC. Consequently,
it is imperative that pilots make every effort to fulfill the
above expected actions to aid ATC in safely handling and
expediting traffic.
e. If the altitude information of an ATC
DESCENT clearance includes a provision to
“CROSS (fix) AT” or “AT OR ABOVE/BELOW
(altitude),” the manner in which the descent is
executed to comply with the crossing altitude is at the
pilot's discretion. This authorization to descend at
pilot's discretion is only applicable to that portion of
the flight to which the crossing altitude restriction
applies, and the pilot is expected to comply with the
crossing altitude as a provision of the clearance. Any
other clearance in which pilot execution is optional
will so state “AT PILOT'S DISCRETION.”
EXAMPLE-
1. “United Four Seventeen, descend and maintain
sixthousand.”
NOTE-
1. The pilot is expected to commence descent upon receipt
of the clearance and to descend at the suggested rates until
reaching the assigned altitude of 6,000 feet.
EXAMPLE-
2. “United Four Seventeen, descend at pilot's discretion,
maintain six thousand.”
NOTE-
2. The pilot is authorized to conduct descent within the
context of the term at pilot's discretion as described above.
EXAMPLE-
3. “United Four Seventeen, cross Lakeview V-O-R at or
above Flight Level two zero zero, descend and maintain
sixthousand.”
NOTE-
3. The pilot is authorized to conduct descent at pilot's
discretion until reaching Lakeview VOR and must comply
with the clearance provision to cross the Lakeview VOR at
or above FL 200. After passing Lakeview VOR, the pilot is
expected to descend at the suggested rates until reaching
the assigned altitude of 6,000 feet.
EXAMPLE-
4. “United Four Seventeen, cross Lakeview V-O-R at
sixthousand, maintain six thousand.”
NOTE-
4. The pilot is authorized to conduct descent at pilot's
discretion, however, must comply with the clearance
provision to cross the Lakeview VOR at 6,000 feet.
EXAMPLE-
5. “United Four Seventeen, descend now to Flight
Leveltwo seven zero, cross Lakeview V-O-R at or below
one zero thousand, descend and maintain six thousand.”
NOTE-
5. The pilot is expected to promptly execute and complete
descent to FL 270 upon receipt of the clearance. After
reaching FL 270 the pilot is authorized to descend “at
pilot's discretion” until reaching Lakeview VOR. The pilot
must comply with the clearance provision to cross
Lakeview VOR at or below 10,000 feet. After Lakeview
VOR the pilot is expected to descend at the suggested rates
until reaching 6,000 feet.
EXAMPLE-
6. “United Three Ten, descend now and maintain Flight
Level two four zero, pilot's discretion after reaching Flight
Level two eight zero.”
NOTE-
6. The pilot is expected to commence descent upon receipt
of the clearance and to descend at the suggested rates until
reaching FL 280. At that point, the pilot is authorized to
continue descent to FL 240 within the context of the term
“at pilot's discretion” as described above.
f. In case emergency authority is used to deviate
from provisions of an ATC clearance, the pilot‐incommand
shall notify ATC as soon as possible and
obtain an amended clearance. In an emergency
situation which does not result in a deviation from the
rules prescribed in 14 CFR Part 91 but which requires
ATC to give priority to an aircraft, the pilot of such
aircraft shall, when requested by ATC, make a report
within 48 hours of such emergency situation to the
manager of that ATC facility.
2/14/08 AIM
ATC Clearances and Aircraft Separation 4-4-7
g. The guiding principle is that the last ATC
clearance has precedence over the previous ATC
clearance. When the route or altitude in a previously
issued clearance is amended, the controller will
restate applicable altitude restrictions. If altitude to
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