There's heights and there heights. The common fear is of heights that are large enough for a fall to cause serious injury, and not too large to be out of range for biological fall protection

I used to be afraid of heights, but trained myself out of it as an adult. I had trouble abseiling, walking on elevated walkways, standing near windows in tall buildings

Three things I never had a height problem with:

• Front seat of a plane (or any other seat, for that matter)
• Basket of a balloon
• On top of a tall hill