When the wind is from the North East, Runway 07R (Zero Seven Right) will always be used by aircraft taking off from Hong Kong International airport (aka Chek Lap Kok, HKIA, HKG, VHHH...)
The aircraft you see from the GZ are all waiting on taxiways Juliet and Hotel (these are like roads for aircraft) for their turn to get airborne.
Once they receive clearance from ATC (Air Traffic Control), they will taxi onto (also called "line-up") the runway using taxiway J1 (pronounced "Juliet One").
Then the Captain will advance the thrust levers to "spool up" the engines and you will hear a magnificent roar as the aircraft accelerates down the runway and lift off on it's way to somewhere in the Big Wide World!
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If you happen to take a photo of an aircraft from GZ, be sure to include it in your log. Who knows, maybe the CO will wave to you from the cockpit window!!