My RC transmitter has a movable antenna that allows me to change its orientation, like this one:
In what direction should I point my 2.4 GHz RC transmitter antenna for best range and signal penetration?
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The antenna should be aligned to match the orientation of the antenna on your aircraft; generally this will be vertical, but for more acrobatic aircraft a compromise of 45° might be appropriate for greater reliability but lower performance. For more detail see this question.
Some manufacturers of off-the-shelf equipment will recommend an orientation in their user manuals - in this case, follow the instructions they give.