4/20/23 

AIM 

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

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1. 

“United Four Seventeen, descend and maintain six thousand.” 

NOTE

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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

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2. 

“United Four Seventeen, descend at pilot’s discretion, maintain six thousand.” 

NOTE

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2. 

The pilot is authorized to conduct descent within the context of the term at pilot’s discretion as described above. 

EXAMPLE

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3. 

“United Four Seventeen, cross Lakeview V

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O

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R at or above Flight Level two zero zero, descend and maintain 

six thousand.” 

NOTE

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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

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4. 

“United Four Seventeen, cross Lakeview V

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O

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R at six thousand, maintain six thousand.” 

NOTE

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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

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5. 

“United Four Seventeen, descend now to Flight Level two seven zero, cross Lakeview V

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O

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R at or below one zero 

thousand, descend and maintain six thousand.” 

NOTE

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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

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6. 

“United Three Ten, descend now and maintain Flight Level two four zero, pilot’s discretion after reaching Flight Level 

two eight zero.” 

NOTE

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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

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in

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command 

must 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 must, when requested by ATC, make a report within 48 hours of such 

emergency situation to the manager of that ATC facility. 

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 maintain is changed or restated, whether prior to departure or while airborne, and 

previously issued altitude restrictions are omitted, those altitude restrictions are canceled, including departure 

procedures and STAR altitude restrictions. 

EXAMPLE

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1. 

A departure flight receives a clearance to destination airport to maintain FL 290. The clearance incorporates a DP which 

ATC Clearances and Aircraft Separation 

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