As the runway crossing are critical situations, when the pilot is instructed to hold, a simple "wilco" or "roger" is not enough for read back, it is essential that the pilot repeats "holding", "holding position" or "holding short".
ICAO Doc 4444
12.3.4.8 HOLDING
‡d) HOLD SHORT OF (position);
*e) HOLDING;
*f) HOLDING SHORT.
‡ Requires specific acknowledgement from the pilot.
* Denotes pilot transmission. The procedure words ROGER and WILCO are insufficient acknowledgement of the instructions HOLD, HOLD POSITION and HOLD SHORT OF (position). In each case the acknowledgement shall be by the phraseology HOLDING or HOLDING SHORT, as appropriate.
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