AIM Text
Tower controllers establish the sequence of arriving and departing aircraft by requiring them to adjust flight or ground operation as necessary to achieve proper spacing. They may “HOLD” an aircraft short of the runway to achieve spacing between it and an arriving aircraft; the controller may instruct a pilot to “EXTEND DOWNWIND” in order to establish spacing from an arriving or departing aircraft. At times a clearance may include the word “IMMEDIATE.” For example: “CLEARED FOR IMMEDIATE TAKEOFF.” In such cases “IMMEDIATE” is used for purposes of air traffic separation. It is up to the pilot to refuse the clearance if, in the pilot's opinion, compliance would adversely affect the operation.
Source: FAA Aeronautical Information Manual · current edition · paragraph 4-4-13.
The short answer
This AIM section is FAA advisory guidance explaining how tower controllers establish the sequence of arriving and departing aircraft by adjusting flight or ground operations for proper spacing. It covers instructions such as HOLD short, EXTEND DOWNWIND, and clearances using IMMEDIATE, and notes the pilot may refuse a clearance that would adversely affect the operation.
Research Notes
Common Questions
What does “CLEARED FOR IMMEDIATE TAKEOFF” mean?
Per the AIM, when a clearance includes the word IMMEDIATE, it is used for purposes of air traffic separation. It is up to the pilot to refuse the clearance if, in the pilot's opinion, compliance would adversely affect the operation.
How does a tower achieve spacing between my aircraft and arriving traffic?
The AIM explains controllers may HOLD an aircraft short of the runway to achieve spacing between it and an arriving aircraft, or instruct a pilot to EXTEND DOWNWIND to establish spacing from an arriving or departing aircraft. These are part of how tower controllers establish the sequence by requiring aircraft to adjust flight or ground operation.
Can I decline an immediate clearance?
Yes. This advisory guidance states it is up to the pilot to refuse the clearance if, in the pilot's opinion, compliance would adversely affect the operation. IMMEDIATE is used only for air traffic separation, not to compel an unsafe action.