Hi Ralphy, Its all a matter of split second timing... If you are waiting at a holding point before entering the runway, you must give way to airplanes who are on Final. Then enter the runway after they pass your location.
Once you are on the runway, you have the right of way, and further aircraft wanting to land must wait for you to depart, as two aircraft are not allowed on one runway together.
It can get a bit hectic at times on a busy GA airfield, with planes landing a few seconds after the other has lifted off.
The only time two or more aircraft are allowed on one runway, is when they are taxiing, and this is best done by agreeing their intentions on the radio first.
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