An ATC route clearance is not an instruction to take off or enter an active runway. The word “TAKEOFF” is used only when an aircraft is cleared for takeoff, or when cancelling a takeoff clearance. At other times the word “DEPARTURE” or “AIRBORNE” is used.
OO-ABC CLEARED TO VALENCIENNES VIA FLIGHT PLANNED ROUTE 4000 FEET SQUAWK 3456
CLEARED TO VALENCIENNES VIA FLIGHT PLANNED ROUTE 4000 FEET SQUAWK 3456 OO-ABC
If an aircraft readback of a clearance or instruction is incorrect, the controller will transmit the word “NEGATIVE” followed by the correct version.
NEGATIVE QNH 1006
If at any time a pilot receives a clearance or instruction which cannot be complied with, the pilot should advise the controller using the word “UNABLE” and give the reasons.
OO-ABC CROSS GREENVILLE FL290 OR ABOVE
UNABLE TO CROSS GREENVILLE FL290 DUE VISIBILITY
Conditional phrases, such as “BEHIND LANDING AIRCRAFT”, or AFTER DEPARTING AIRCRAFT” should not be used for movements affecting the active runway(s), except when the aircraft or vehicles concerned are seen by the controller and the pilot.
The aircraft or vehicle causing the condition in the clearance should be the first aircraft/vehicle to pass in front of the aircraft receiving the conditional clearance.
In all cases a conditional clearance will be given in the following order and consist of:
b) the condition;
c) the clearance;
d) brief reiteration of the condition.
OO ABC, BEHIND CESSNA 172 ON SHORT FINAL, LINE UP BEHIND
FASTFLY 123, AFTER DEPARTING BOEING 737, LINE UP BEHIND
These require the aircraft receiving the conditional clearance to identify the aircraft or vehicle causing the condition and not accept the clearance until this is achieved.