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AIM

10/12/17

4−4−6

ATC Clearances and Aircraft Separation

is authorized to conduct the climb or descent at any

rate, and to temporarily level off at any intermediate

altitude as desired. However, once the aircraft has

vacated an altitude, it may not return to that altitude.

d. When ATC has not used the term “AT PILOT’S

DISCRETION” nor imposed any climb or descent

restrictions, pilots should initiate climb or descent

promptly on acknowledgement of the clearance.

Descend or climb at an optimum rate consistent with

the operating characteristics of the aircraft to

1,000 feet above or below the assigned altitude, and

then attempt to descend or climb at a rate of between

500 and 1,500 fpm until the assigned altitude is

reached. If at anytime the pilot is unable to climb or

descend at a rate of at least 500 feet a minute, advise

ATC. If it is necessary to level off at an intermediate

altitude during climb or descent, advise ATC, except

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.

NOTE−

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) to comply with 14 CFR

Section 91.117 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

six thousand.”

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

six thousand.”
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

six thousand, 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

Level two 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−in−