What is an example of the phraseology used for amending an altitude in a previously issued clearance?

• A. UNITED SIX SIXTY SIX, CHANGE ALTITUDE. CROSS OLLIS INTERSECTION AT OR ABOVE THREE THOUSAND, CROSS GORDONSVILLE V-O-R AT OR ABOVE ONE TWO THOUSAND. MAINTAIN FLIGHT LEVEL TWO FOUR ZERO
• B. UNITED SIX SIXTY SIX, CANCEL PREVIOUS ALTITUDE. CROSS OLLIS INTERSECTION AT OR ABOVE THREE THOUSAND, CROSS GORDONSVILLE V-O-R AT OR ABOVE ONE TWO THOUSAND. MAINTAIN FLIGHT LEVEL TWO FOUR ZERO.
• C. UNITED SIX SIXTY SIX, AMEND ALTITUDE. CROSS OLLIS INTERSECTION AT OR ABOVE THREE THOUSAND, CROSS GORDONSVILLE V-O-R AT OR ABOVE ONE TWO THOUSAND. MAINTAIN FLIGHT LEVEL TWO FOUR ZERO.
• D. UNITED SIX SIXTY SIX, AMEND CLEARANCE. CROSS OLLIS INTERSECTION AT OR ABOVE THREE THOUSAND, CROSS GORDONSVILLE V-O-R AT OR ABOVE ONE TWO THOUSAND. MAINTAIN FLIGHT LEVEL TWO FOUR ZERO.

Answer: (C)

When you need to change only the altitude in an existing clearance, you use the exact phrase “amend altitude.” This signals that all other parts of the clearance—route, speed, crossing points, and other instructions—remain in effect while the altitude is updated. In this scenario, the controller is shifting the aircraft’s altitude requirements (cross Ollis at or above 3,000 and cross Gordonsville VOR at or above 12,000, then continue at FL240) without altering the rest of the clearance, so saying “amend altitude” is the precise, standard way to convey that change.

Other phrasings would imply different actions: “cancel previous altitude” would drop the altitude element without providing a replacement, which isn’t the intended action here. “Amend clearance” would modify more than just the altitude, and would not specifically indicate updating the altitude portion alone. “Amend altitude” is the targeted, correct expression for changing only the altitude while keeping the rest of the clearance intact.