The fact that air pressure is lower at higher altitudes or in airplanes is relevant to your research question because it means that the amount of air pressure can affect how far a soccer ball travels when kicked. In general, the higher the air pressure, the more force the air exerts on the soccer ball, which can cause it to travel a greater distance. Conversely, the lower the air pressure, the less force the air exerts on the soccer ball, which can cause it to travel a shorter distance.
Therefore, if you were to conduct a study on how the amount of air pressure affects the distance a soccer ball travels when kicked, you would need to take into account the fact that air pressure is lower at higher altitudes or in airplanes. This could be done by measuring the air pressure at the location where the soccer ball is kicked, and comparing it to the baseline air pressure at sea level to determine the relative air pressure. You could then use this information to calculate the expected distance the soccer ball should travel based on the amount of air pressure present. This would help ensure that your results are accurate and can be compared to other studies on this topic.